Method and apparatus for transmitting channel state information in wireless access system supporting machine type communication

ABSTRACT

The present invention provides a method by which an MTC terminal measures channel state information (CSI), a method for transmitting CSI, and apparatuses supporting the same. A method by which the MTC terminal feeds back CSI in a wireless access system supporting machine type communication (MTC), according to one embodiment of the present invention, comprises the steps of: receiving allocation information on a limited MTC bandwidth allocated to the MTC terminal calculating CSI; and feeding back the CSI. Here, the CSI can include MTC wideband channel state information (MTC W-CQI) for the limited MTC bandwidth.

TECHNICAL FIELD

The present invention relates to a wireless access system supportingmachine type communication (MTC) and, more particularly, to a method ofmeasuring channel status information (CSI) at an MTC user equipment(UE), a method of transmitting CSI, and an apparatus supporting thesame.

BACKGROUND ART

Wireless access systems have been widely deployed to provide varioustypes of communication services such as voice or data. In general, awireless access system is a multiple access system that supportscommunication of multiple users by sharing available system resources (abandwidth, transmission power, etc.) among them. For example, multipleaccess systems include a Code Division Multiple Access (CDMA) system, aFrequency Division Multiple Access (FDMA) system, a Time DivisionMultiple Access (TDMA) system, an Orthogonal Frequency Division MultipleAccess (OFDMA) system, and a Single Carrier Frequency Division MultipleAccess (SC-FDMA) system.

DISCLOSURE Technical Problem

An object of the present invention is to provide a method of efficientlymeasuring channel status information (CSI) and a method of reporting CSIat a low-cost MTC UE.

Another object of the present invention is to provide methods ofperiodically or aperiodically reporting CSI at a low-cost MTC UE.

Another object of the present invention is to provide a method ofefficiently measuring and reporting CSI at an MTC UE by newly definingan MTC bandwidth for a low-cost MTC UE only in a restricted area unlikea legacy bandwidth.

Another object of the present invention is to provide apparatusessupporting such methods .

It will be appreciated by persons skilled in the art that the objectsthat could be achieved with the present invention are not limited towhat has been particularly described hereinabove and the above and otherobjects that the present invention could achieve will be more clearlyunderstood from the following detailed description.

Technical Solution

The present invention proposes a method of measuring channel statusinformation (CSI) at an MTC user equipment (UE), a method oftransmitting CSI, and apparatus supporting the same.

As an aspect of the present invention, a method of feeding back channelstatus information (CSI) at a machine type communication (MTC) userequipment (UE) in a wireless access system supporting MTC includesreceiving allocation information of a limited MTC bandwidth allocated tothe MTC UE, calculating the CSI, and feeding back the CSI. At this time,the CSI includes MTC wideband channel status information (W-CQI) for thelimited MTC bandwidth.

As another aspect of the present invention, machine type communication(MTC) user equipment (UE) for feeding back channel status information(CSI) in a wireless access system supporting MTC includes a transmitter,a receiver, and a processor configured to control the transmitter andthe receiver to support the feedback of the CSI. At this time, theprocessor is configured to control the receiver to receive allocationinformation of a limited MTC bandwidth allocated to the MTC UE,calculate the CSI and control the transmitter to feed back the CSI. Atthis time, the CSI includes MTC wideband channel status information(W-CQI) for the limited MTC bandwidth.

The allocation information of the limited MTC bandwidth may besemi-statically transmitted through a system information block (SIB)message or may be dynamically transmitted in every subframe through aphysical downlink control channel (PDCCH) or an enhanced physicaldownlink control channel (EPDCCH).

The feeding back the CSI may be aperiodically performed when a requestof a base station is received, and the size of the limited MTC bandwidthmay be set to 7 or fewer resource blocks (RBs).

The feeding back the CSI may be periodically performed, and the size ofthe limited MTC bandwidth may be set to 7 or fewer resource blocks(RBs).

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

Advantageous Effects

As is apparent from the above description, the embodiments of thepresent invention have the following effects.

First, an MTC UE can efficiently measure and report CSI by newlydefining an MTC bandwidth for a low-cost MTC UE only in a restrictedarea unlike a legacy bandwidth.

Second, when a low-cost MTC UE periodically or aperiodically reportsCSI, it is possible to decrease the amount of reported CSI as comparedto legacy methods.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the technical features or scope of theinventions. Thus, it is intended that the present invention covers themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention.

FIG. 1 is a conceptual diagram illustrating physical channels used inthe embodiments and a signal transmission method using the physicalchannels.

FIG. 2 is a diagram illustrating a structure of a radio frame for use inthe embodiments.

FIG. 3 is a diagram illustrating an example of a resource grid of adownlink slot according to the embodiments.

FIG. 4 is a diagram illustrating a structure of an uplink subframeaccording to the embodiments.

FIG. 5 is a diagram illustrating a structure of a downlink subframeaccording to the embodiments.

FIG. 6 illustrates PUCCH formats 1a and 1b for use in a normal cyclicprefix (CP) case, and FIG. 7 illustrates PUCCH formats 1a and 1b for usein an extended CP case.

FIG. 8 illustrates PUCCH formats 2/2a/2b in a normal cyclic prefix (CP)case, and FIG. 9 illustrates PUCCH formats 2/2a/2b in an extended CPcase.

FIG. 10 illustrates ACK/NACK channelization for PUCCH formats 1a and 1b.

FIG. 11 illustrates channelization for a hybrid structure of PUCCHformat 1a/1b and format 2/2a/2b in the same PRB.

FIG. 12 illustrates allocation of a physical resource block (PRB).

FIG. 13 is a diagram illustrating an example of a component carrier (CC)of the embodiments and carrier aggregation (CA) used in an LTE_A system.

FIG. 14 illustrates a subframe structure of an LTE-A system according tocross-carrier scheduling.

FIG. 15 is conceptual diagram illustrating a construction of servingcells according to cross-carrier scheduling.

FIG. 16 is a conceptual diagram illustrating CA PUCCH signal processing.

FIG. 17 is a diagram showing a process of performing the methodsdescribed in section 4.3.

FIG. 18 is a diagram showing a process of performing the methodsdescribed in section 4.4.

FIG. 19 is a diagram showing means for implementing the methodsdescribed with reference to FIGS. 1 to 18.

BEST MODE

The embodiments of the present invention described in detail belowdisclose a method of measuring channel status information (CSI) at alow-cost MTC UE, a method of transmitting CSI and apparatuses supportingthe same, in a wireless access system supporting machine typecommunication (MTC).

The embodiments of the present disclosure described below arecombinations of elements and features of the present disclosure inspecific forms. The elements or features may be considered selectiveunless otherwise mentioned. Each element or feature may be practicedwithout being combined with other elements or features. Further, anembodiment of the present disclosure may be constructed by combiningparts of the elements and/or features. Operation orders described inembodiments of the present disclosure may be rearranged. Someconstructions or elements of any one embodiment may be included inanother embodiment and may be replaced with corresponding constructionsor features of another embodiment.

In the description of the attached drawings, a detailed description ofknown procedures or steps of the present disclosure will be avoided lestit should obscure the subject matter of the present disclosure. Inaddition, procedures or steps that could be understood to those skilledin the art will not be described either.

Throughout the specification, when a certain portion “includes” or“comprises” a certain component, this indicates that other componentsare not excluded and may be further included unless otherwise noted. Theterms “unit”, “-or/er” and “module” described in the specificationindicate a unit for processing at least one function or operation, whichmay be implemented by hardware, software or a combination thereof. Inaddition, the terms “a or an”, “one”, “the” etc. may include a singularrepresentation and a plural representation in the context of the presentinvention (more particularly, in the context of the following claims)unless indicated otherwise in the specification or unless contextclearly indicates otherwise.

In the embodiments of the present disclosure, a description is mainlymade of a data transmission and reception relationship between a BaseStation (BS) and a User Equipment (UE). A BS refers to a terminal nodeof a network, which directly communicates with a UE. A specificoperation described as being performed by the BS may be performed by anupper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with a fixed station, aNode B, an evolved Node B (eNode B or eNB), an Advanced Base Station(ABS), an access point, etc.

In the embodiments of the present disclosure, the term terminal may bereplaced with a UE, a Mobile Station (MS), a Subscriber Station (SS), aMobile Subscriber Station (MSS), a mobile terminal, an Advanced MobileStation (AMS), etc.

A transmitter is a fixed and/or mobile node that provides a data serviceor a voice service and a receiver is a fixed and/or mobile node thatreceives a data service or a voice service. Therefore, a UE may serve asa transmitter and a BS may serve as a receiver, on an UpLink (UL).Likewise, the UE may serve as a receiver and the BS may serve as atransmitter, on a DownLink (DL).

The embodiments of the present disclosure may be supported by standardspecifications disclosed for at least one of wireless access systemsincluding an Institute of Electrical and Electronics Engineers (IEEE)802.xx system, a 3^(rd) Generation Partnership Project (3GPP) system, a3GPP Long Term Evolution (LTE) system, and a 3GPP2 system. Inparticular, the embodiments of the present disclosure may be supportedby the standard specifications, 3GPP TS 36.211, 3GPP TS 36.212, 3GPP TS36.213, 3GPP TS 36.321 and 3GPP TS 36.331. That is, the steps or parts,which are not described to clearly reveal the technical idea of thepresent disclosure, in the embodiments of the present disclosure may beexplained by the above standard specifications. All terms used in theembodiments of the present disclosure may be explained by the standardspecifications.

Reference will now be made in detail to the embodiments of the presentdisclosure with reference to the accompanying drawings. The detaileddescription, which will be given below with reference to theaccompanying drawings, is intended to explain exemplary embodiments ofthe present disclosure, rather than to show the only embodiments thatcan be implemented according to the invention.

The following detailed description includes specific terms in order toprovide a thorough understanding of the present disclosure. However, itwill be apparent to those skilled in the art that the specific terms maybe replaced with other terms without departing the technical spirit andscope of the present disclosure.

Hereinafter, 3GPP LTE/LTE-A systems which are examples of a wirelessaccess system which can be applied to embodiments to the presentinvention will be explained.

The embodiments of the present disclosure can be applied to variouswireless access systems such as Code Division Multiple Access (CDMA),Frequency Division Multiple Access (FDMA), Time Division Multiple Access(TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), SingleCarrier Frequency Division Multiple Access (SC-FDMA), etc.

CDMA may be implemented as a radio technology such as UniversalTerrestrial Radio Access (UTRA) or CDMA2000. TDMA may be implemented asa radio technology such as Global System for Mobile communications(GSM)/General packet Radio Service (GPRS)/Enhanced Data Rates for GSMEvolution (EDGE). OFDMA may be implemented as a radio technology such asIEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Evolved UTRA(E-UTRA), etc.

UTRA is a part of Universal Mobile Telecommunications System (UMTS).3GPP LTE is a part of Evolved UMTS (E-UMTS) using E-UTRA, adopting OFDMAfor DL and SC-FDMA for UL. LTE-Advanced (LTE-A) is an evolution of 3GPPLTE. While the embodiments of the present disclosure are described inthe context of a 3GPP LTE/LTE-A system in order to clarify the technicalfeatures of the present disclosure, the present disclosure is alsoapplicable to an IEEE 802.16e/m system, etc.

1. 3GPP LTE/LTE-A System

In a wireless access system, a UE receives information from an eNB on aDL and transmits information to the eNB on a UL. The informationtransmitted and received between the UE and the eNB includes generaldata information and various types of control information. There aremany physical channels according to the types/usages of informationtransmitted and received between the eNB and the UE.

1.1 System Overview

FIG. 1 illustrates physical channels and a general method using thephysical channels, which may be used in embodiments of the presentdisclosure.

When a UE is powered on or enters a new cell, the UE performs initialcell search (S11). The initial cell search involves acquisition ofsynchronization to an eNB. Specifically, the UE synchronizes its timingto the eNB and acquires information such as a cell Identifier (ID) byreceiving a Primary Synchronization Channel (P-SCH) and a SecondarySynchronization Channel (S-SCH) from the eNB.

Then the UE may acquire information broadcast in the cell by receiving aPhysical Broadcast Channel (PBCH) from the eNB.

During the initial cell search, the UE may monitor a DL channel state byreceiving a Downlink Reference Signal (DL RS).

After the initial cell search, the UE may acquire more detailed systeminformation by receiving a Physical Downlink Control Channel (PDCCH) andreceiving a Physical Downlink Shared Channel (PDSCH) based oninformation of the PDCCH (S12).

To complete connection to the eNB, the UE may perform a random accessprocedure with the eNB (S13 to S16). In the random access procedure, theUE may transmit a preamble on a Physical Random Access Channel (PRACH)(S13) and may receive a PDCCH and a PDSCH associated with the PDCCH(S14). In the case of contention-based random access, the UE mayadditionally perform a contention resolution procedure includingtransmission of an additional PRACH (S15) and reception of a PDCCHsignal and a PDSCH signal corresponding to the PDCCH signal (S16).

After the above procedure, the UE may receive a PDCCH and/or a PDSCHfrom the eNB (S17) and transmit a Physical Uplink Shared Channel (PUSCH)and/or a Physical Uplink Control Channel (PUCCH) to the eNB (S18), in ageneral UL/DL signal transmission procedure.

Control information that the UE transmits to the eNB is genericallycalled Uplink Control Information (UCI). The UCI includes a HybridAutomatic Repeat and reQuest Acknowledgement/Negative Acknowledgement(HARQ-ACK/NACK), a Scheduling Request (SR), a Channel Quality Indicator(CQI), a Precoding Matrix Index (PMI), a Rank Indicator (RI), etc.

In the LTE system, UCI is generally transmitted on a PUCCH periodically.However, if control information and traffic data should be transmittedsimultaneously, the control information and traffic data may betransmitted on a PUSCH. In addition, the UCI may be transmittedaperiodically on the PUSCH, upon receipt of a request/command from anetwork.

FIG. 2 illustrates exemplary radio frame structures used in embodimentsof the present disclosure.

FIG. 2(a) illustrates frame structure type 1. Frame structure type 1 isapplicable to both a full Frequency Division Duplex (FDD) system and ahalf FDD system.

One radio frame is 10 ms (T_(f)=307200·T_(s)) long, includingequal-sized 20 slots indexed from 0 to 19. Each slot is 0.5 ms(T_(slot)=15360·T_(s)) long. One subframe includes two successive slots.An i^(th) subframe includes 2i^(th) and (2i+1)^(th) slots. That is, aradio frame includes 10 subframes. A time required for transmitting onesubframe is defined as a Transmission Time Interval (TTI). T_(s) is asampling time given as T_(s)=1/(15 kHz×2048)=3.2552×10⁻⁸ (about 33 ns).One slot includes a plurality of Orthogonal Frequency DivisionMultiplexing (OFDM) symbols or SC-FDMA symbols in the time domain by aplurality of Resource Blocks (RBs) in the frequency domain.

A slot includes a plurality of OFDM symbols in the time domain. SinceOFDMA is adopted for DL in the 3GPP LTE system, one OFDM symbolrepresents one symbol period. An OFDM symbol may be called an SC-FDMAsymbol or symbol period. An RB is a resource allocation unit including aplurality of contiguous subcarriers in one slot.

In a full FDD system, each of 10 subframes may be used simultaneouslyfor DL transmission and UL transmission during a 10 -ms duration. The DLtransmission and the UL transmission are distinguished by frequency. Onthe other hand, a UE cannot perform transmission and receptionsimultaneously in a half FDD system.

The above radio frame structure is purely exemplary. Thus, the number ofsubframes in a radio frame, the number of slots in a subframe, and thenumber of OFDM symbols in a slot may be changed.

FIG. 2(b) illustrates frame structure type 2. Frame structure type 2 isapplied to a Time Division Duplex (TDD) system. One radio frame is 10 ms(T_(f)=307200·T_(s)) long, including two half-frames each having alength of 5 ms (=153600·T_(s)) long. Each half-frame includes fivesubframes each being 1 ms (=30720·T_(s)) long. An i^(th) subframeincludes 2i^(th) and (2i+1)^(th) slots each having a length of 0.5 ms(T_(slot)=15360·T_(s)). T_(s) is a sampling time given asT_(s)=1/(15kHz×2048)=3.2552×10⁻⁸ (about 33 ns).

A type-2 frame includes a special subframe having three fields, DownlinkPilot Time Slot (DwPTS), Guard Period (GP), and Uplink Pilot Time Slot(UpPTS). The DwPTS is used for initial cell search, synchronization, orchannel estimation at a UE, and the UpPTS is used for channel estimationand UL transmission synchronization with a UE at an eNB. The GP is usedto cancel UL interference between a UL and a DL, caused by themulti-path delay of a DL signal.

[Table 1] below lists special subframe configurations (DwPTS/GP/UpPTSlengths).

TABLE 1 Normal cyclic prefix in downlink Extended cyclic prefix indownlink UpPTS UpPTS Special Normal Extended Normal Extended subframecyclic prefix cyclic prefix cyclic prefix cyclic prefix configurationDwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192· T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 ·T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600· T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592· T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 ·T_(s) 7 21952 · T_(s) — — — 8 24144 · T_(s) — — —

FIG. 3 illustrates an exemplary structure of a DL resource grid for theduration of one DL slot, which may be used in embodiments of the presentdisclosure.

Referring to FIG. 3, a DL slot includes a plurality of OFDM symbols inthe time domain. One DL slot includes 7 OFDM symbols in the time domainand an RB includes 12 subcarriers in the frequency domain, to which thepresent disclosure is not limited.

Each element of the resource grid is referred to as a Resource Element(RE). An RB includes 12×7 REs. The number of RBs in a DL slot, N_(DL)depends on a DL transmission bandwidth. A UL slot may have the samestructure as a DL slot.

FIG. 4 illustrates a structure of a UL subframe which may be used inembodiments of the present disclosure.

Referring to FIG. 4, a UL subframe may be divided into a control regionand a data region in the frequency domain. A PUCCH carrying UCI isallocated to the control region and a PUSCH carrying user data isallocated to the data region. To maintain a single carrier property, aUE does not transmit a PUCCH and a PUSCH simultaneously. A pair of RBsin a subframe are allocated to a PUCCH for a UE. The RBs of the RB pairoccupy different subcarriers in two slots. Thus it is said that the RBpair frequency-hops over a slot boundary.

FIG. 5 illustrates a structure of a DL subframe that may be used inembodiments of the present disclosure.

Referring to FIG. 5, up to three OFDM symbols of a DL subframe, startingfrom OFDM symbol 0 are used as a control region to which controlchannels are allocated and the other OFDM symbols of the DL subframe areused as a data region to which a PDSCH is allocated. DL control channelsdefined for the 3GPP LTE system include a Physical Control FormatIndicator Channel (PCFICH), a PDCCH, and a Physical Hybrid ARQ IndicatorChannel (PHICH).

The PCFICH is transmitted in the first OFDM symbol of a subframe,carrying information about the number of OFDM symbols used fortransmission of control channels (i.e. the size of the control region)in the subframe. The PHICH is a response channel to a UL transmission,delivering an HARQ ACK/NACK signal. Control information carried on thePDCCH is called Downlink Control Information (DCI). The DCI transportsUL resource assignment information, DL resource assignment information,or UL Transmission (Tx) power control commands for a UE group.

1.2 Physical Downlink Control Channel (PDCCH)

1.2.1 PDCCH Overview

The PDCCH may deliver information about resource allocation and atransport format for a Downlink Shared Channel (DL-SCH) (i.e. a DLgrant), information about resource allocation and a transport format foran Uplink Shared Channel (UL-SCH) (i.e. a UL grant), paging informationof a Paging Channel (PCH), system information on the DL-SCH, informationabout resource allocation for a higher layer control message such as arandom access response transmitted on the PDSCH, a set of Tx powercontrol commands for individual UEs of a UE group, Voice Over InternetProtocol (VoIP) activation indication information, etc.

A plurality of PDCCHs may be transmitted in the control region. A UE maymonitor a plurality of PDCCHs. A PDCCH is transmitted in an aggregate ofone or more consecutive Control Channel Elements (CCEs). A PDCCH made upof one or more consecutive CCEs may be transmitted in the control regionafter subblock interleaving. A CCE is a logical allocation unit used toprovide a PDCCH at a code rate based on the state of a radio channel. ACCE includes a plurality of RE Groups (REGs). The format of a PDCCH andthe number of available bits for the PDCCH are determined according tothe relationship between the number of CCEs and a code rate provided bythe CCEs.

1.2.2 PDCCH Structure

A plurality of PDCCHs for a plurality of UEs may be multiplexed andtransmitted in the control region. A PDCCH is made up of an aggregate ofone or more consecutive CCEs. A CCE is a unit of 9 REGs each REGincluding 4 REs. Four Quadrature Phase Shift Keying (QPSK) symbols aremapped to each REG. REs occupied by RSs are excluded from REGs. That is,the total number of REGs in an OFDM symbol may be changed depending onthe presence or absence of a cell-specific RS. The concept of an REG towhich four REs are mapped is also applicable to other DL controlchannels (e.g. the PCFICH or the PHICH). Let the number of REGs that arenot allocated to the PCFICH or the PHICH be denoted by N_(REG). Then thenumber of CCEs available to the system is N_(CCE) (=└N_(REG)19┘) and theCCEs are indexed from 0 to N_(CCE)−1.

To simplify the decoding process of a UE, a PDCCH format including nCCEs may start with a CCE having an index equal to a multiple of n. Thatis, given CCE i, the PDCCH format may start with a CCE satisfying i modn=0.

The eNB may configure a PDCCH with 1, 2, 4, or 8 CCEs. {1, 2, 4, 8} arecalled CCE aggregation levels. The number of CCEs used for transmissionof a PDCCH is determined according to a channel state by the eNB. Forexample, one CCE is sufficient for a PDCCH directed to a UE in a good DLchannel state (a UE near to the eNB). On the other hand, 8 CCEs may berequired for a PDCCH directed to a UE in a poor DL channel state (a UEat a cell edge) in order to ensure sufficient robustness.

[Table 2] below illustrates PDCCH formats. 4 PDCCH formats are supportedaccording to CCE aggregation levels as illustrated in [Table 2].

TABLE 2 PDCCH Number of Number of Number of format CCEs (n) REGs PDCCHbits 0 1 9 72 1 2 18 144 2 4 36 288 3 8 72 576

A different CCE aggregation level is allocated to each UE because theformat or Modulation and Coding Scheme (MCS) level of controlinformation delivered in a PDCCH for the UE is different. An MCS leveldefines a code rate used for data coding and a modulation order. Anadaptive MCS level is used for link adaptation. In general, three orfour MCS levels may be considered for control channels carrying controlinformation.

Regarding the formats of control information, control informationtransmitted on a PDCCH is called DCI. The configuration of informationin PDCCH payload may be changed depending on the DCI format. The PDCCHpayload is information bits. [Table 3] lists DCI according to DCIformats.

TABLE 3 DCI Format Description Format 0 Resource grants for the PUSCHtransmissions (uplink) Format 1 Resource assignments for single codewordPDSCH transmissions (transmission modes 1, 2 and 7) Format 1A Compactsignaling of resource assignments for single codeword PDSCH (all modes)Format 1B Compact resource assignments for PDSCH using rank-1 closedloop precoding (mode 6) Format 1C Very compact resource assignments forPDSCH (e.g. paging/broadcast system information) Format 1D Compactresource assignments for PDSCH using multi-user MIMO (mode 5) Format 2Resource assignments for PDSCH for closed-loop MIMO operation (mode 4)Format 2A Resource assignments for PDSCH for open-loop MIMO operation(mode 3) Format 3/3A Power control commands for PUCCH and PUSCH with2-bit/1-bit power adjustment Format 4 Scheduling of PUSCH in one UL cellwith multi-antenna port transmission mode

Referring to [Table 3], the DCI formats include Format 0 for PUSCHscheduling, Format 1 for single-codeword PDSCH scheduling, Format 1A forcompact single-codeword PDSCH scheduling, Format 1C for very compactDL-SCH scheduling, Format 2 for PDSCH scheduling in a closed-loopspatial multiplexing mode, Format 2A for PDSCH scheduling in anopen-loop spatial multiplexing mode, and Format 3/3A for transmission ofTransmission Power Control (TPC) commands for uplink channels. DCIFormat 1A is available for PDSCH scheduling irrespective of thetransmission mode of a UE.

The length of PDCCH payload may vary with DCI formats. In addition, thetype and length of PDCCH payload may be changed depending on compact ornon-compact scheduling or the transmission mode of a UE.

The transmission mode of a UE may be configured for DL data reception ona PDSCH at the UE. For example, DL data carried on a PDSCH includesscheduled data, a paging message, a random access response, broadcastinformation on a BCCH, etc. for a UE. The DL data of the PDSCH isrelated to a DCI format signaled through a PDCCH. The transmission modemay be configured semi-statically for the UE by higher layer signaling(e.g. Radio Resource Control (RRC) signaling). The transmission mode maybe classified as single antenna transmission or multi-antennatransmission.

A transmission mode is configured for a UE semi-statically by higherlayer signaling. For example, multi-antenna transmission scheme mayinclude transmit diversity, open-loop or closed-loop spatialmultiplexing, Multi-User Multiple Input Multiple Output (MU-MIMO), orbeamforming. Transmit diversity increases transmission reliability bytransmitting the same data through multiple Tx antennas. Spatialmultiplexing enables high-speed data transmission without increasing asystem bandwidth by simultaneously transmitting different data throughmultiple Tx antennas. Beamforming is a technique of increasing theSignal to Interference plus Noise Ratio (SINR) of a signal by weightingmultiple antennas according to channel states.

A DCI format for a UE depends on the transmission mode of the UE. The UEhas a reference DCI format monitored according to the transmission modeconfigure for the UE. The following 10 transmission modes are availableto UEs:

(1)Transmission mode 1: Single antenna port (port 0);

(2) Transmission mode 2: Transmit diversity;

(3) Transmission mode 3: Open-loop spatial multiplexing when the numberof layer is larger than 1 or Transmit diversity when the rank is 1;

(4) Transmission mode 4: Closed-loop spatial multiplexing;

(5) Transmission mode 5: MU-MIMO;

(6) Transmission mode 6: Closed-loop rank-1 precoding;

(7) Transmission mode 7: Precoding supporting a single layertransmission, which does not based on a codebook (Rel-8);

(8) Transmission mode 8: Precoding supporting up to two layers, which donot based on a codebook (Rel-9);

(9) Transmission mode 9: Precoding supporting up to eight layers, whichdo not based on a codebook (Rel-10); and

(10) Transmission mode 10: Precoding supporting up to eight layers,which do not based on a codebook, used for CoMP (Rel-11).

1.2.3 PDCCH Transmission

The eNB determines a PDCCH format according to DCI that will betransmitted to the UE and adds a Cyclic Redundancy Check (CRC) to thecontrol information. The CRC is masked by a unique Identifier (ID) (e.g.a Radio Network Temporary Identifier (RNTI)) according to the owner orusage of the PDCCH. If the PDCCH is destined for a specific UE, the CRCmay be masked by a unique ID (e.g. a cell-RNTI (C-RNTI)) of the UE. Ifthe PDCCH carries a paging message, the CRC of the PDCCH may be maskedby a paging indicator ID (e.g. a Paging-RNTI (P-RNTI)). If the PDCCHcarries system information, particularly, a System Information Block(SIB), its CRC may be masked by a system information ID (e.g. a SystemInformation RNTI (SI-RNTI)). To indicate that the PDCCH carries a randomaccess response to a random access preamble transmitted by a UE, its CRCmay be masked by a Random Access-RNTI (RA-RNTI).

Then the eNB generates coded data by channel-encoding the CRC-addedcontrol information. The channel coding may be performed at a code ratecorresponding to an MCS level. The eNB rate-matches the coded dataaccording to a CCE aggregation level allocated to a PDCCH format andgenerates modulation symbols by modulating the coded data. Herein, amodulation order corresponding to the MCS level may be used for themodulation. The CCE aggregation level for the modulation symbols of aPDCCH may be one of 1, 2, 4, and 8. Subsequently, the eNB maps themodulation symbols to physical REs (i.e. CCE to RE mapping).

1.2.4 Blind Decoding (BD)

A plurality of PDCCHs may be transmitted in a subframe. That is, thecontrol region of a subframe includes a plurality of CCEs, CCE 0 to CCEN_(CCE)-1, N_(CCE,k) is the total number of CCEs in the control regionof a k^(th) subframe. A UE monitors a plurality of PDCCHs in everysubframe. This means that the UE attempts to decode each PDCCH accordingto a monitored PDCCH format.

The eNB does not provide the UE with information about the position of aPDCCH directed to the UE in an allocated control region of a subframe.Without knowledge of the position, CCE aggregation level, or DCI formatof its PDCCH, the UE searches for its PDCCH by monitoring a set of PDCCHcandidates in the subframe in order to receive a control channel fromthe eNB. This is called blind decoding. Blind decoding is the process ofdemasking a CRC part with a UE ID, checking a CRC error, and determiningwhether a corresponding PDCCH is a control channel directed to a UE bythe UE.

The UE monitors a PDCCH in every subframe to receive data transmitted tothe UE in an active mode. In a Discontinuous Reception (DRX) mode, theUE wakes up in a monitoring interval of every DRX cycle and monitors aPDCCH in a subframe corresponding to the monitoring interval. ThePDCCH-monitored subframe is called a non-DRX subframe.

To receive its PDCCH, the UE should blind-decode all CCEs of the controlregion of the non-DRX subframe. Without knowledge of a transmitted PDCCHformat, the UE should decode all PDCCHs with all possible CCEaggregation levels until the UE succeeds in blind-decoding a PDCCH inevery non-DRX subframe. Since the UE does not know the number of CCEsused for its PDCCH, the UE should attempt detection with all possibleCCE aggregation levels until the UE succeeds in blind decoding of aPDCCH.

In the LTE system, the concept of Search Space (SS) is defined for blinddecoding of a UE. An SS is a set of PDCCH candidates that a UE willmonitor. The SS may have a different size for each PDCCH format. Thereare two types of SSs, Common Search Space (CSS) andUE-specific/Dedicated Search Space (USS).

While all UEs may know the size of a CSS, a USS may be configured foreach individual UE. Accordingly, a UE should monitor both a CSS and aUSS to decode a PDCCH. As a consequence, the UE performs up to 44 blinddecodings in one subframe, except for blind decodings based on differentCRC values (e.g., C-RNTI, P-RNTI, SI-RNTI, and RA-RNTI).

In view of the constraints of an SS, the eNB may not secure CCEresources to transmit PDCCHs to all intended UEs in a given subframe.This situation occurs because the remaining resources except forallocated CCEs may not be included in an SS for a specific UE. Tominimize this obstacle that may continue in the next subframe, aUE-specific hopping sequence may apply to the starting point of a USS.

[Table 4] illustrates the sizes of CSSs and USSs.

TABLE 4 Number of Number of PDCCH Number of candidates in candidates informat CCEs (n) common search space dedicated search space 0 1 — 6 1 2 —6 2 4 4 2 3 8 2 2

To mitigate the load of the UE caused by the number of blind decodingattempts, the UE does not search for all defined DCI formatssimultaneously. Specifically, the UE always searches for DCI Format 0and DCI Format 1A in a USS. Although DCI Format 0 and DCI Format 1A areof the same size, the UE may distinguish the DCI formats by a flag forformat0/format 1a differentiation included in a PDCCH. Other DCI formatsthan DCI Format 0 and DCI Format 1A, such as DCI Format 1, DCI Format1B, and DCI Format 2 may be required for the UE.

The UE may search for DCI Format 1A and DCI Format 1C in a CSS. The UEmay also be configured to search for DCI Format 3 or 3A in the CSS.Although DCI Format 3 and DCI Format 3A have the same size as DCI Format0 and DCI Format 1A, the UE may distinguish the DCI formats by a CRCscrambled with an ID other than a UE-specific ID.

An SS S_(k) ^((L)) is a PDCCH candidate set with a CCE aggregation levelL∈{1,2,4,8}. The CCEs of PDCCH candidate set m in the SS may bedetermined by the following equation.

L·{(Y _(k) +m) mod└N _(CCE,k) /L┘}+i   [Equation 1]

where M^((L)) is the number of PDCCH candidates with CCE aggregationlevel L to be monitored in the SS, m+0, . . . , M^((L))−1, i is theindex of a CCE in each PDCCH candidate, and i=0, . . . , L−1 k=└n_(s)/2┘where n_(s) is the index of a slot in a radio frame.

As described before, the UE monitors both the USS and the CSS to decodea PDCCH. The CSS supports PDCCHs with CCE aggregation levels {4, 8} andthe USS supports PDCCHs with CCE aggregation levels {1, 2, 4, 8}. [Table5] illustrates PDCCH candidates monitored by a UE.

TABLE 5 Search space S_(k) ^((L)) Aggregation Size Number of PDCCH Typelevel L [in CCEs] candidates M^((L)) UE- 1 6 6 specific 2 12 6 4 8 2 816 2 Common 4 16 4 8 16 2

Referring to [Equation 1], for two aggregation levels, L=4 and L=8, isset to 0 in the CSS, whereas Y_(k) is defined by [Equation 2] foraggregation level L in the USS.

Y _(k)=(A·Y _(k−1)) mod D   [Equation 2]

where Y⁻¹=n_(RNTI)≠0, n_(RNTI) indicating an RNTI value. A=39827 andD=65537.

1.3. PUCCH (Physical Uplink Control Channel)

PUCCH may include the following formats to transmit control information.

(1) Format 1: On-Off keying (OOK) modulation, used for SR (SchedulingRequest)

(2) Format 1a & 1b: Used for ACK/NACK transmission

-   -   1) Format 1a: BPSK ACK/NACK for 1 codeword    -   2) Format 1b: QPSK ACK/NACK for 2 codewords

(3) Format 2: QPSK modulation, used for CQI transmission

(4) Format 2a & Format 2b: Used for simultaneous transmission of CQI andACK/NACK

(5) Format 3: Used for multiple ACK/NACK transmission in a carrieraggregation environment

Table 6 shows a modulation scheme according to PUCCH format and thenumber of bits per subframe. Table 7 shows the number of referencesignals (RS) per slot according to PUCCH format. Table 8 shows SC-FDMAsymbol location of RS (reference signal) according to PUCCH format. InTable 6, PUCCH format 2a and PUCCH format 2b correspond to a case ofnormal cyclic prefix (CP).

TABLE 6 PUCCH Modulation No. of bits per format scheme subframe, Mbit 1 N/A N/A 1a BPSK 1 1b QPSK 2 2  QPSK 20 2a QPSK + BPSK 21 2b QPSK + BPSK22 3  QPSK 48

TABLE 7 PUCCH format Normal CP Extended CP 1, 1a, 1b 3 2 2, 3 2 1 2a, 2b2 N/A

TABLE 8 PUCCH SC-FDMA symbol location of RS format Normal CP Extended CP1, 1a, 1b 2, 3, 4 2, 3 2, 3 1, 5 3 2a, 2b 1, 5 N/A

FIG. 6 shows PUCCH formats 1a and 1b in case of a normal cyclic prefix.And, FIG. 7 shows PUCCH formats 1a and 1b in case of an extended cyclicprefix.

According to the PUCCH formats 1a and 1b, control information of thesame content is repeated in a subframe by slot unit. In each userequipment, ACK/NACK signal is transmitted on a different resourceconstructed with a different cyclic shift (CS) (frequency domain code)and an orthogonal cover (OC) or orthogonal cover code (OCC) (time domainspreading code) of CG-CAZAC (computer-generated constant amplitude zeroauto correlation) sequence. For instance, the OC includes Walsh/DFTorthogonal code. If the number of CS and the number of OC are 6 and 3,respectively, total 18 user equipments may be multiplexed within thesame PRB (physical resource block) with reference to a single antenna.Orthogonal sequences w0, w1, w2 and w3 may be applicable to a randomtime domain (after FFT modulation) or a random frequency domain (beforeFFT modulation).

For persistent scheduling with SR, ACK/NACK resource constructed withCS, OC and PRB (physical resource block) may be allocated to a userequipment through RRC (radio resource control. For non-persistentscheduling with dynamic ACK/NACK, the ACK/NACK resource may beimplicitly allocated to a user equipment using a smallest CCE index ofPDCCH corresponding to PDSCH.

Length-4 orthogonal sequence (OC) and length-3 orthogonal sequence forPUCCH format 1/1a/1b are shown in Table 9 and Table 10, respectively.

TABLE 9 Sequence Orthogonal sequences index n_(oc)(n_(s)) [w(0) . . .w(N_(SF) ^(PUCCH) − 1)] 0 [+1 +1 +1 +1] 1 [+1 −1 +1 −1] 2 [+1 −1 −1 +1]

TABLE 10 Sequence Orthogonal sequences index n_(oc)(n_(s)) [w(0) . . .w(N_(SF) ^(PUCCH) − 1)] 0 [1 1 1] 1 [1 e^(j2π/3) e^(j4π/3)] 2 [1e^(j4π/3) e^(j2π/3)]

Orthogonal sequence (OC) [w(0) . . . w(N_(RS) ^(PUCCH)−1)] for areference signal in PUCCH format 1/1a/1b is shown in Table 11.

TABLE 11 Sequence Normal cyclic Extended cyclic index n _(oc)(n_(s))prefix prefix 0 [1 1 1] [1 1] 1 [1 e^(j2π/3) e^(j4π/3)] [1 −1] 2 [1e^(j4π/3) e^(j2π/3)] N/A

FIG. 8 shows PUCCH format 2/2a/2b in case of a normal cyclic prefix.And, FIG. 9 shows PUCCH format 2/2a/2b in case of an extended cyclicprefix.

Referring to FIG. 8 and FIG. 9, in case of a normal CP, a subframe isconstructed with 10 QPSK data symbols as well as RS symbol. Each QPSKsymbol is spread in a frequency domain by CS and is then mapped to acorresponding SC-FDMA symbol. SC-FDMA symbol level CS hopping may beapplied to randomize inter-cell interference. The RS may be multiplexedby CDM using a cyclic shift. For instance, assuming that the number ofavailable CSs is 12, 12 user equipments may be multiplexed in the samePRB. For instance, assuming that the number of available CSs is 6, 6user equipments may be multiplexed in the same PRB. In brief, aplurality of user equipments in PUCCH format 1/1a/1b and PUCCH format2/2a/2b may be multiplexed by ‘CS+OC+PRB’ and ‘CS+PRB’, respectively.

FIG. 10 is a diagram of ACK/NACK channelization for PUCCH formats 1a and1b. In particular, FIG. 10 corresponds to a case of ‘Δ_(shift)^(PUCCH)=2’

FIG. 11 is a diagram of channelization for a hybrid structure of PUCCHformat 1/1a/1b and PUCCH format 2/2a/2b.

Cyclic shift (CS) hopping and orthogonal cover (OC) remapping may beapplicable in a following manner.

(1) Symbol-based cell-specific CS hopping for randomization ofinter-cell interference

(2) Slot level CS/OC remapping

-   -   1) For inter-cell interference randomization    -   2) Slot based access for mapping between ACK/NACK channel and        resource (k)

Meanwhile, resource n_(r) for PUCCH format 1/1a/1b may include thefollowing combinations.

(1) CS (=equal to DFT orthogonal code at symbol level) (n_(cs))

(2) OC (orthogonal cover at slot level) (n_(oc))

(3) Frequency RB (Resource Block) (n_(rb))

If indexes indicating CS, OC and RB are set to n_(cs), n_(oc), n_(rb),respectively, a representative index n_(r) may include n_(cs), n_(oc)and n_(rb). In this case, the n_(r) may meet the condition of‘n_(r)=(n_(cs), n_(oc), n_(rb))’.

The combination of CQI, PMI, RI, CQI and ACK/NACK may be deliveredthrough the PUCCH format 2/2a/2b. And, Reed Muller (RM) channel codingmay be applicable.

For instance, channel coding for UL (uplink) CQI in LTE system may bedescribed as follows. First of all bitstreams α₀, α₁, α₂, α₃, . . . ,α_(A-1) may be coded using (20, A) RM code. In this case, α_(o) andα_(A-1) indicates MSB (Most Significant Bit) and LSB (Least SignificantBit), respectively. In case of an extended cyclic prefix, maximuminformation bits include 11 bits except a case that QI and ACK/NACK aresimultaneously transmitted. After coding has been performed with 20 bitsusing the RM code, QPSK modulation may be applied. Before the BPSKmodulation, coded bits may be scrambled.

Table 12 shows a basic sequence for (20, A) code.

TABLE 12 i M_(i, 0) M_(i, 1) M_(i, 2) M_(i, 3) M_(i, 4) M_(i, 5)M_(i, 6) M_(i, 7) M_(i, 8) M_(i, 9) M_(i, 10) M_(i, 11) M_(i, 12) 0 1 10 0 0 0 0 0 0 0 1 1 0 1 1 1 1 0 0 0 0 0 0 1 1 1 0 2 1 0 0 1 0 0 1 0 1 11 1 1 3 1 0 1 1 0 0 0 0 1 0 1 1 1 4 1 1 1 1 0 0 0 1 0 0 1 1 1 5 1 1 0 01 0 1 1 1 0 1 1 1 6 1 0 1 0 1 0 1 0 1 1 1 1 1 7 1 0 0 1 1 0 0 1 1 0 1 11 8 1 1 0 1 1 0 0 1 0 1 1 1 1 9 1 0 1 1 1 0 1 0 0 1 1 1 1 10 1 0 1 0 0 11 1 0 1 1 1 1 11 1 1 1 0 0 1 1 0 1 0 1 1 1 12 1 0 0 1 0 1 0 1 1 1 1 1 113 1 1 0 1 0 1 0 1 0 1 1 1 1 14 1 0 0 0 1 1 0 1 0 0 1 0 1 15 1 1 0 0 1 11 1 0 1 1 0 1 16 1 1 1 0 1 1 1 0 0 1 0 1 1 17 1 0 0 1 1 1 0 0 1 0 0 1 118 1 1 0 1 1 1 1 1 0 0 0 0 0 19 1 0 0 0 0 1 1 0 0 0 0 0 0

Channel coding bits b₀, b₁, b₂, b₃, . . . , b_(B-1) may be generated byFormula 1.

$\begin{matrix}{b_{i} = {\sum\limits_{n - 0}^{A - 1}\; {( {a_{n} \cdot M_{i,n}} ){mod}\; 2}}} & \lbrack {{Formula}\mspace{14mu} 3} \rbrack\end{matrix}$

In Formula 3, ‘i=0, 1, 2, . . . , B-1’ is met.

In case of wideband repots, a bandwidth of UCI (uplink controlinformation) field for CQI/PMI can be represented as Tables 8 to 10 inthe following.

Table 13 shows UCI (Uplink Control Information) field for broadbandreport (single antenna port, transmit diversity) or open loop spatialmultiplexing PDSCH CQI feedback.

TABLE 13 Field Bandwidth Broadband CQI 4

Table 14 shows UL control information (UCI) field for CQI and PMIfeedback in case of wideband reports (closed loop spatial multiplexingPDSCH transmission).

TABLE 14 Bandwidth 2 antenna ports 4 antenna ports Field rank = 1 rank =2 rank = 1 Rank > 1 Wideband CQI 4 4 4 4 Spatial differential 0 3 0 3CQI Precoding Matrix 2 1 4 4 Indication

Table 15 shows UL control information (UCI) field for RI feedback incase of wideband reports.

TABLE 15 Bit widths 4 antenna ports Field 2 antenna ports Max. 2 layersMax. 4 layers Rank Indication 1 1 2

FIG. 12 is a diagram for PRB allocation. Referring to FIG. 20, PRB maybe usable for PUCCH transmission in a slot

2. Carrier Aggregation (CA) Environment

2.1 CA Overview

A 3GPP LTE system (conforming to Rel-8 or Rel-9) (hereinafter, referredto as an LTE system) uses Multi-Carrier Modulation (MCM) in which asingle Component Carrier (CC) is divided into a plurality of bands. Incontrast, a 3GPP LTE-A system (hereinafter, referred to an LTE-A system)may use CA by aggregating one or more CCs to support a broader systembandwidth than the LTE system. The term CA is interchangeably used withcarrier combining, multi-CC environment, or multi-carrier environment.

In the present disclosure, multi-carrier means CA (or carriercombining). Herein, CA covers aggregation of contiguous carriers andaggregation of non-contiguous carriers. The number of aggregated CCs maybe different for a DL and a UL. If the number of DL CCs is equal to thenumber of UL CCs, this is called symmetric aggregation. If the number ofDL CCs is different from the number of UL CCs, this is called asymmetricaggregation. The term CA is interchangeable with carrier combining,bandwidth aggregation, spectrum aggregation, etc.

The LTE-A system aims to support a bandwidth of up to 100 MHz byaggregating two or more CCs, that is, by CA. To guarantee backwardcompatibility with a legacy IMT system, each of one or more carriers,which has a smaller bandwidth than a target bandwidth, may be limited toa bandwidth used in the legacy system.

For example, the legacy 3GPP LTE system supports bandwidths {1.4, 3, 5,10, 15, and 20 MHz} and the 3GPP LTE-A system may support a broaderbandwidth than 20 MHz using these LTE bandwidths. A CA system of thepresent disclosure may support CA by defining a new bandwidthirrespective of the bandwidths used in the legacy system.

There are two types of CA, intra-band CA and inter-band CA. Intra-bandCA means that a plurality of DL CCs and/or UL CCs are successive oradjacent in frequency. In other words, the carrier frequencies of the DLCCs and/or UL CCs are positioned in the same band. On the other hand, anenvironment where CCs are far away from each other in frequency may becalled inter-band CA. In other words, the carrier frequencies of aplurality of DL CCs and/or UL CCs are positioned in different bands. Inthis case, a UE may use a plurality of Radio Frequency (RF) ends toconduct communication in a CA environment.

The LTE-A system adopts the concept of cell to manage radio resources.The above-described CA environment may be referred to as a multi-cellenvironment. A cell is defined as a pair of DL and UL CCs, although theUL resources are not mandatory. Accordingly, a cell may be configuredwith DL resources alone or DL and UL resources.

For example, if one serving cell is configured for a specific UE, the UEmay have one DL CC and one UL CC. If two or more serving cells areconfigured for the UE, the UE may have as many DL CCs as the number ofthe serving cells and as many UL CCs as or fewer UL CCs than the numberof the serving cells, or vice versa. That is, if a plurality of servingcells are configured for the UE, a CA environment using more UL CCs thanDL CCs may also be supported.

CA may be regarded as aggregation of two or more cells having differentcarrier frequencies (center frequencies). Herein, the term ‘cell’ shouldbe distinguished from ‘cell’ as a geographical area covered by an eNB.Hereinafter, intra-band CA is referred to as intra-band multi-cell andinter-band CA is referred to as inter-band multi-cell.

In the LTE-A system, a Primacy Cell (PCell) and a Secondary Cell (SCell)are defined. A PCell and an SCell may be used as serving cells. For a UEin RRC_CONNECTED state, if CA is not configured for the UE or the UEdoes not support CA, a single serving cell including only a PCell existsfor the UE. On the contrary, if the UE is in RRC_CONNECTED state and CAis configured for the UE, one or more serving cells may exist for theUE, including a PCell and one or more SCells.

Serving cells (PCell and SCell) may be configured by an RRC parameter. Aphysical-layer ID of a cell, PhysCellId is an integer value ranging from0 to 503. A short ID of an SCell, SCellIndex is an integer value rangingfrom 1 to 7. A short ID of a serving cell (PCell or SCell),ServeCellIndex is an integer value ranging from 1 to 7. IfServeCellIndex is 0, this indicates a PCell and the values ofServeCellIndex for SCells are pre-assigned. That is, the smallest cellID (or cell index) of ServeCellIndex indicates a PCell.

A PCell refers to a cell operating in a primary frequency (or a primaryCC). A UE may use a PCell for initial connection establishment orconnection reestablishment. The PCell may be a cell indicated duringhandover. In addition, the PCell is a cell responsible forcontrol-related communication among serving cells configured in a CAenvironment. That is, PUCCH allocation and transmission for the UE maytake place only in the PCell. In addition, the UE may use only the PCellin acquiring system information or changing a monitoring procedure. AnEvolved Universal Terrestrial Radio Access Network (E-UTRAN) may changeonly a PCell for a handover procedure by a higher layerRRCConnectionReconfiguraiton message including mobilityControlInfo to aUE supporting CA.

An SCell may refer to a cell operating in a secondary frequency (or asecondary CC). Although only one PCell is allocated to a specific UE,one or more SCells may be allocated to the UE. An SCell may beconfigured after RRC connection establishment and may be used to provideadditional radio resources. There is no PUCCH in cells other than aPCell, that is, in SCells among serving cells configured in the CAenvironment.

When the E-UTRAN adds an SCell to a UE supporting CA, the E-UTRAN maytransmit all system information related to operations of related cellsin RRC_CONNECTED state to the UE by dedicated signaling. Changing systeminformation may be controlled by releasing and adding a related SCell.Herein, a higher layer RRCConnectionReconfiguration message may be used.The E-UTRAN may transmit a dedicated signal having a different parameterfor each cell rather than it broadcasts in a related SCell.

After an initial security activation procedure starts, the E-UTRAN mayconfigure a network including one or more SCells by adding the SCells toa PCell initially configured during a connection establishmentprocedure. In the CA environment, each of a PCell and an SCell mayoperate as a CC. Hereinbelow, a Primary CC (PCC) and a PCell may be usedin the same meaning and a Secondary CC (SCC) and an SCell may be used inthe same meaning in embodiments of the present disclosure.

FIG. 13 illustrates an example of CCs and CA in the LTE-A system, whichare used in embodiments of the present disclosure.

FIG. 13(a) illustrates a single carrier structure in the LTE system.There are a DL CC and a UL CC and one CC may have a frequency range of20 MHz.

FIG. 13(b) illustrates a CA structure in the LTE-A system. In theillustrated case of FIG. 13(b), three CCs each having 20 MHz areaggregated. While three DL CCs and three UL CCs are configured, thenumbers of DL CCs and UL CCs are not limited. In CA, a UE may monitorthree CCs simultaneously, receive a DL signal/DL data in the three CCs,and transmit a UL signal/UL data in the three CCs.

If a specific cell manages N DL CCs, the network may allocate M DL CCsto a UE. The UE may monitor only the M DL CCs and receive a DL signal inthe M DL CCs. The network may prioritize L DL CCs and allocate a main DLCC to the UE. In this case, the UE should monitor the L DL CCs. The samething may apply to UL transmission.

The linkage between the carrier frequencies of DL resources (or DL CCs)and the carrier frequencies of UL resources (or UL CCs) may be indicatedby a higher layer message such as an RRC message or by systeminformation. For example, a set of DL resources and UL resources may beconfigured based on linkage indicated by System Information Block Type 2(SIB2). Specifically, DL-UL linkage may refer to a mapping relationshipbetween a DL CC carrying a PDCCH with a UL grant and a UL CC using theUL grant, or a mapping relationship between a DL CC (or a UL CC)carrying HARQ data and a UL CC (or a DL CC) carrying an HARQ ACK/NACKsignal.

2.2 Cross Carrier Scheduling

Two scheduling schemes, self-scheduling and cross carrier scheduling aredefined for a CA system, from the perspective of carriers or servingcells. Cross carrier scheduling may be called cross CC scheduling orcross cell scheduling.

In self-scheduling, a PDCCH (carrying a DL grant) and a PDSCH aretransmitted in the same DL CC or a PUSCH is transmitted in a UL CClinked to a DL CC in which a PDCCH (carrying a UL grant) is received.

In cross carrier scheduling, a PDCCH (carrying a DL grant) and a PDSCHare transmitted in different DL CCs or a PUSCH is transmitted in a UL CCother than a UL CC linked to a DL CC in which a PDCCH (carrying a ULgrant) is received.

Cross carrier scheduling may be activated or deactivated UE-specificallyand indicated to each UE semi-statically by higher layer signaling (e.g.RRC signaling).

If cross carrier scheduling is activated, a Carrier Indicator Field(CIF) is required in a PDCCH to indicate a DL/UL CC in which aPDSCH/PUSCH indicated by the PDCCH is to be transmitted. For example,the PDCCH may allocate PDSCH resources or PUSCH resources to one of aplurality of CCs by the CIF. That is, when a PDCCH of a DL CC allocatesPDSCH or PUSCH resources to one of aggregated DL/UL CCs, a CIF is set inthe PDCCH. In this case, the DCI formats of LTE Release-8 may beextended according to the CIF. The CIF may be fixed to three bits andthe position of the CIF may be fixed irrespective of a DCI format size.In addition, the LTE Release-8 PDCCH structure (the same coding andresource mapping based on the same CCEs) may be reused.

On the other hand, if a PDCCH transmitted in a DL CC allocates PDSCHresources of the same DL CC or allocates PUSCH resources in a single ULCC linked to the DL CC, a CIF is not set in the PDCCH. In this case, theLTE Release-8 PDCCH structure (the same coding and resource mappingbased on the same CCEs) may be used.

If cross carrier scheduling is available, a UE needs to monitor aplurality of PDCCHs for DCI in the control region of a monitoring CCaccording to the transmission mode and/or bandwidth of each CC.Accordingly, an appropriate SS configuration and PDCCH monitoring areneeded for the purpose.

In the CA system, a UE DL CC set is a set of DL CCs scheduled for a UEto receive a PDSCH, and a UE UL CC set is a set of UL CCs scheduled fora UE to transmit a PUSCH. A PDCCH monitoring set is a set of one or moreDL CCs in which a PDCCH is monitored. The PDCCH monitoring set may beidentical to the UE DL CC set or may be a subset of the UE DL CC set.The PDCCH monitoring set may include at least one of the DL CCs of theUE DL CC set. Or the PDCCH monitoring set may be defined irrespective ofthe UE DL CC set. DL CCs included in the PDCCH monitoring set may beconfigured to always enable self-scheduling for UL CCs linked to the DLCCs. The UE DL CC set, the UE UL CC set, and the PDCCH monitoring setmay be configured UE-specifically, UE group-specifically, orcell-specifically.

If cross carrier scheduling is deactivated, this implies that the PDCCHmonitoring set is always identical to the UE DL CC set. In this case,there is no need for signaling the PDCCH monitoring set. However, ifcross carrier scheduling is activated, the PDCCH monitoring set may bedefined within the UE DL CC set. That is, the eNB transmits a PDCCH onlyin the PDCCH monitoring set to schedule a PDSCH or PUSCH for the UE.

FIG. 14 illustrates a cross carrier-scheduled subframe structure in theLTE-A system, which is used in embodiments of the present disclosure.

Referring to FIG. 14, three DL CCs are aggregated for a DL subframe forLTE-A UEs. DL CC ‘A’ is configured as a PDCCH monitoring DL CC. If a CIFis not used, each DL CC may deliver a PDCCH that schedules a PDSCH inthe same DL CC without a CIF. On the other hand, if the CIF is used byhigher layer signaling, only DL CC ‘A’ may carry a PDCCH that schedulesa PDSCH in the same DL CC ‘A’ or another CC. Herein, no PDCCH istransmitted in DL CC ‘B’ and DL CC ‘C’ that are not configured as PDCCHmonitoring DL CCs.

FIG. 15 is conceptual diagram illustrating a construction of servingcells according to cross-carrier scheduling.

Referring to FIG. 15, an eNB (or BS) and/or UEs for use in a radioaccess system supporting carrier aggregation (CA) may include one ormore serving cells. In FIG. 8, the eNB can support a total of fourserving cells (cells A, B, C and D). It is assumed that UE A may includeCells (A, B, C), UE B may include Cells (B, C, D), and UE C may includeCell B. In this case, at least one of cells of each UE may be composedof P Cell. In this case, P Cell is always activated, and S Cell may beactivated or deactivated by the eNB and/or UE.

The cells shown in FIG. 15 may be configured per UE. The above-mentionedcells selected from among cells of the eNB, cell addition may be appliedto carrier aggregation (CA) on the basis of a measurement report messagereceived from the UE. The configured cell may reserve resources forACK/NACK message transmission in association with PDSCH signaltransmission. The activated cell is configured to actually transmit aPDSCH signal and/or a PUSCH signal from among the configured cells, andis configured to transmit CSI reporting and Sounding Reference Signal(SRS) transmission. The deactivated cell is configured not totransmit/receive PDSCH/PUSCH signals by an eNB command or a timeroperation, and CRS reporting and SRS transmission are interrupted.

2.3 CA PUCCH (Carrier Aggregation Physical Uplink Control Channel)

In a wireless communication system supportive of carrier aggregation,PUCCH format for feeding back UCI (e.g., multi-ACK/NACK bit) can bedefined. For clarity of the following description, such PUCCH formatshall be named CA PUCCH format.

FIG. 16 is a diagram for one example of a signal processing process ofCA PUCCH.

Referring to FIG. 16, a channel coding block generates coding bits(e.g., encoded bits, coded bits, etc.) (or codeword) b_0, b_1, . . . andb_N-1 by channel-coding information bits a_0, a_1, . . . and a_M-1(e.g., multiple ACK/NACK bits). In this case, the M indicates a size ofinformation bits and the N indicates a size of the coding bits. Theinformation bits may include multiple ACK/NACK for UL controlinformation (UCI), e.g., a plurality of data (or PDSCH) received via aplurality of DL CCS. In this case, the information bits a_0, a_1, . . .a_M-1 may be joint-coded irrespective of type/number/size of the UCIconfiguring the information bits. For instance, in case that informationbits include multiple ACK/NACK for a plurality of DL CCs, channel codingmay not be performed per DL CC or individual ACK/NACK bit but may beperformed on all bit information, from which a single codeword may begenerated. And, channel coding is non-limited by this. Moreover, thechannel coding may include one of simplex repetition, simplex coding, RM(Reed Muller) coding, punctured RM coding, TBCC (tail-bitingconvolutional coding), LDPC (low-density parity-check), turbo coding andthe like. Besides, coding bits may be rate-matched in consideration of amodulation order and a resource size (not shown in the drawing). A ratematching function may be included as a part of the channel coding blockor may be performed via a separate function block.

A modulator generates modulated symbols c_0, c_1 . . . c_L-1 bymodulating coding bits b_0, b_1 . . . b N-1. In this case, the Lindicates a size of modulated symbol. This modulation scheme may beperformed in a manner of modifying a size and phase of a transmissionsignal. For instance, the modulation scheme may include one of n-PSK(Phase Shift Keying), n-QAM (Quadrature Amplitude Modulation) and thelike, where n is an integer equal to or greater than 2. In particular,the modulation scheme may include one of BPSK (Binary PSK), QPSK(Quadrature PSK), 8-PSK, QAM, 16-QAM, 64-QAM and the like.

A divider divides the modulated symbols c_0, c_1 . . . c_L-1 to slots,respectively. A sequence/pattern/scheme for dividing the modulatedsymbols to the slots may be specially non-limited. For instance, thedivider may be able to divide the modulated symbols to the correspondingslots in order from a head to tail (Localized scheme). In doing so, asshown in the drawing, the modulated symbols c_0, c_1 . . . c_L/2-1 maybe divided to the slot 0 and the modulated symbols c_L/2, c_L/2+1 . . .c_L-1 may be divided to the slot 1. Moreover, the modulated symbols maybe divided to the corresponding slots, respectively, by interleaving orpermutation. For instance, the even-numbered modulated symbol may bedivided to the slot 0, while the odd-numbered modulated symbol may bedivided to the slot 1. The modulation scheme and the dividing scheme maybe switched to each other in order.

A DFT precoder may perform DFT precoding (e.g., 12-point DFT) on themodulated symbols divided to the corresponding slots to generate asingle carrier waveform. Referring to the drawing, the modulated symbolsc_0, c_1 . . . c_L/2-1 divided to the corresponding slot 0 may beDFT-precoded into DFT symbols d_0, d_1 . . . d_L/2-1, and the modulatedsymbols c_L/2, c_L/2+1 . . . c_L-1 divided to the slot 1 may beDFT-precoded into DFT symbols d_L/2, d_L/2+1 . . . d_L-1. Moreover, theDFT precoding may be replaced by another linear operation (e.g., Walshprecoding) corresponding thereto.

A spreading block may spread the DFT-performed signal at SC-FDMA symbolslevel (e.g., time domain). The time-domain spreading at the SC-FDMAlevel may be performed using a spreading code (sequence). The spreadingcode may include pseudo orthogonal code and orthogonal code. The pseudoorthogonal code may include PN (pseudo noise) code, by which the pseudoorthogonal code may be non-limited. The orthogonal code may includeWalsh code and DFT code, by which the orthogonal code may benon-limited. The orthogonal code (OC) may be interchangeably used withone of an orthogonal sequence, an orthogonal cover (OC) and anorthogonal cover code (OCC). In this specification, for example, theorthogonal code may be mainly described as a representative example ofthe spreading code for clarity and convenience of the followingdescription. Optionally, the orthogonal code may be substituted with thepseudo orthogonal code. A maximum value of a spreading code size (or aspreading factor: SF) may be limited by the number of SC-FDAM symbolsused for control information transmission. For example, in case that 5SC-FDMA symbols are used in one slot for control informationtransmission, orthogonal codes (or pseudo orthogonal codes) w0, w1, w2,w3 and w4 of length 5 may be used per slot. The SF may mean a spreadingdegree of the control information and may be associated with amultiplexing order or an antenna multiplexing order of a user equipment.The SF may be variable like 1, 2, 3, 4, 5 . . . depending on arequirement of a system. The SF may be defined in advance between a basestation and a user equipment. And, the SF may be notified to a userequipment via DCI or RRC signaling.

The signal generated through the above-described process may be mappedto subcarrier within the PRB and may be then transformed into atime-domain signal through IFFT. CP may be attached to the time-domainsignal. The generated SC-FDMA symbol may be then transmitted through anRF stage.

3. Method for feeding back Channel State Information (CSI)

3.1 Channel State Information (CSI)

First of all, in the 3GPP LTE system, when a DL reception entity (e.g.,a user equipment) is connected to a DL transmission entity (e.g., a basestation), the DL reception entity performs measurement on a referencesignal received power (RSRP) of a reference signal transmitted in DL, aquality of a reference signal (RSRQ: reference signal received quality)and the like at a random time and is then able to make a periodic oreven-triggered report of a corresponding measurement result to the basestation.

Each user equipment reports a DL channel information in accordance witha DL channel status via uplink. A base station is then able to determinetime/frequency resources, MCS (modulation and coding scheme) and thelike appropriate for a data transmission to each user equipment usingthe DL channel information received from the each user equipment.

Such channel state information (CSI) may include CQI (Channel QualityIndication), PMI (Precoding Matrix Indicator), PTI (Precoder TypeIndication) and/or RI (Rank Indication). In particular, the CSI may betransmitted entirely or partially depending on a transmission mode ofeach user equipment. CQI is determined based on a received signalquality of a user equipment, which may be generally determined on thebasis of a measurement of a DL reference signal. In doing so, a CQIvalue actually delivered to a base station may correspond to an MCScapable of providing maximum performance by maintaining a block errorrate (BLER) under 10% in the received signal quality measured by a userequipment.

This channel information reporting may be classified into a periodicreport transmitted periodically and an aperiodic report transmitted inresponse to a request made by a base station.

In case of the aperiodic report, it is set for each user equipment by a1-bit request bit (CQI request bit) contained in UL schedulinginformation downloaded to a user equipment by a base station. Havingreceived this information, each user equipment is then able to deliverchannel information to the base station via a physical uplink sharedchannel (PUSCH) in consideration of its transmission mode. And, it mayset RI and CQI/PMI not to be transmitted on the same PUSCH.

In case of the periodic report, a period for transmitting channelinformation via an upper layer signal, an offset in the correspondingperiod and the like are signaled to each user equipment by subframe unitand channel information in consideration of a transmission mode of eachuser equipment may be delivered to a base station via a physical uplinkcontrol channel (PUCCH) in accordance with a determined period. In casethat data transmitted in uplink simultaneously exists in a subframe inwhich channel information is transmitted by a determined period, thecorresponding channel information may be transmitted together with thedata not on the physical uplink control channel (PUCCH) but on aphysical uplink shared channel (PUSCH). In case of the periodic reportvia PUCCH, bits (e.g., 11 bits) limited further than those of the PUSCHmay be used. RI and CQI/PMI may be transmitted on the same PUSCH.

In case that contention occurs between the periodic report and theaperiodic report in the same subframe, only the aperiodic report can beperformed.

In calculating Wideband CQI/PMI, a most recently transmitted RI may beusable. RI in a PUCCH CSI report mode is independent from RI in a PUSCHCSI report mode. The RI in the PUSCH CSI report mode is valid forCQI/PMI in the corresponding PUSCH CSI report mode only.

Table 16 is provided to describe CSI feedback type transmitted on PUCCHand PUCCH CSI report mode.

TABLE 16 PMI Feedback Type No PMI (OL, TD, single-antenna) Single PMI(CL) CQI Wideband Mode 1-0 Mode 1-1 Feedback RI (only for RI TypeOpen-Loop SM) Wideband CQI (4 bit) One Wideband CQI Wideband spatial CQI(4 bit) (3 bit) for RI > 1 when RI > 1, CQI of Wideband PMI (4 bit)first codeword UE Mode 2-0 Mode 2-1 Selected RI (only for RI Open-LoopSM) Wideband CQI (4 bit) Wideband CQI (4 bit) Wideband spatial CQIBest-1 CQI (4 bit) (3 bit) for RI > 1 in each BP Wideband PMI (4 bit)Best-1 indicator Best-1 CQI (4 bit) (L-bit label) 1 in each BP when RI >1, CQI of Best-1 spatial CQI first codeword (3 bit) for RI > 1 Best-1indicator (L-bit label)

Referring to Table 16, in the periodic report of channel information,there are 4 kinds of reporting modes (mode 1-0, mode 1-2, mode 2-0 andmode 2-1) in accordance with CQI and PMI feedback types.

CQI can be classified into WB (wideband) CQI and SB (subband) CQI inaccordance with CQI feedback type and PMI can be classified into No PMIor Single PMI in accordance with a presence or non-presence of PMItransmission. In Table 11, No PMI corresponds to a case of open-loop(OL), transmit diversity (TD) and single-antenna, while Single PMIcorresponds to a case of closed-loop (CL).

The mode 1-0 corresponds to a case that WB CQI is transmitted in theabsence of PMI transmission. In this case, RI is transmitted only incase of open-loop (OL) spatial multiplexing (SM) and one WB CQIrepresented as 4 bits can be transmitted. If RI is greater than 1, CQIfor a 1^(st) codeword can be transmitted.

The mode 1-1 corresponds to a case that a single PMI and WB CQI aretransmitted. In this case, 4-bit WB CQI and 4-bit WB PMI can betransmitted together with RI transmission. Additionally, if RI isgreater than 1, 3-bit WB (wideband) spatial differential CQI can betransmitted. In 2-codeword transmission, the WB spatial differential CQImay indicate a difference value between a WB CQI index for codeword 1and a WB CQI index for codeword 2. The difference value in-between mayhave a value selected from a set {−4, −3, −2, −1, 0, 1, 2, 3} and can berepresented as 3 bits.

The mode 2-0 corresponds to a case that CQI on a UE-selected band istransmitted in the absence of PMI transmission. In this case, RI istransmitted only in case of open-loop spatial multiplexing (SM) and a WBCQI represented as 4 bits may be transmitted. A best CQI (best-1) istransmitted on each bandwidth part (BP) and the best-1 CQI may berepresented as 4 bits. And, an L-bit indicator indicating the best-1 maybe transmitted together. If the RI is greater than 1, a CQI for a 1^(st)codeword can be transmitted.

And, the mode 2-1 corresponds to a case that a single PMI and a CQI on aUE-selected band are transmitted. In this case, together with RItransmission, 4-bit WB CQI, 3-bit WB spiral differential CQI and 4-bitWB PMI can be transmitted. Additionally, 4-bit best-1 CQI is transmittedon each bandwidth part (BP) and L-bit best-1 indicator can betransmitted together. Additionally, if RI is greater than 1, 3-bitbest-1 spatial differential CQI can be transmitted. In 2-codewordtransmission, it may indicate a difference value between a best-1 CQIindex of codeword 1 and a best-1 CQI index of codeword 2.

For the transmission modes, periodic PUCCH CSI report modes aresupported as follows.

1) Transmission mode 1: Modes 1-0 and 2-0

2) Transmission mode 2: Modes 1-0 and 2-0

3) Transmission mode 3: Modes 1-0 and 2-0

4) Transmission mode 4: Modes 1-1 and 2-1

5) Transmission mode 5: Modes 1-1 and 2-1

6) Transmission mode 6: Modes 1-1 and 2-1

7) Transmission mode 7: Modes 1-0 and 2-0

8) Transmission mode 8: Modes 1-1 and 2-1 if a user equipment is set tomake a PMI/RI reporting, or Modes 1-0 and 2-0 if a user equipment is setnot to make a PMI/RI reporting

9) Transmission mode 9: Modes 1-1 and 2-1 if a user equipment is set tomake a PMI/RI reporting and the number of CSI-RS ports is greater than1, or Modes 1-0 and 2-0 if a user equipment is set not to make a PMI/RIreporting and the number of CSI-RS port(s) is equal to 1.

The periodic PUCCH CSIU reporting mode in each serving cell is set byupper layer signaling. And, the mode 1-1 is set to either submode 1 orsubmode 2 by an upper layer signaling using a parameter‘PUCCH_format1-1_CSI_reporting_mode’.

A CQI reporting in a specific subframe of a specific serving cell in aUE-selected SB CQI means a measurement of at least one channel state ofa bandwidth part (BP) corresponding to a portion of a bandwidth of aserving cell. An index is given to the bandwidth part in a frequencyincreasing order starting with a lowest frequency without an incrementof a bandwidth.

3.2 CSI Feedback Method

In an LTE system, an open-loop MIMO scheme operated without channelinformation and a closed-loop MIMO scheme operated based on channelinformation are used. Especially, according to the closed-loop MIMOscheme, each of a transmitter and a receiver may be able to performbeamforming based on channel information (e.g., CSI) to obtain amultiplexing gain of MIMO antennas. To obtain CSI, the eNB allocates aphysical uplink control channel (PUCCH) or a physical uplink sharedchannel (PUSCH) to the UE and instructs the UE to feed back CSI of adownlink channel.

CSI includes Rank Indicator (RI) information, Precoding Matrix Indicator(PMI) information, and Channel Quality Indicator (CQI) information.First, RI indicates rank information of a channel and means the numberof data streams that can be received by the UE via the samefrequency-time resource. Since RI is dominantly determined by long-termfading of a channel, this may be generally fed back from the UE to theeNB at a cycle longer than that of PMI or CQI. PMI is a value to whichthe spatial characteristic of a channel is reflected. PMI indicates aprecoding index of the eNB preferred by the UE based on a metric ofsignal-to-interference plus noise ratio (SINR). Lastly, CQI isinformation indicating the strength of a channel and generally indicatesa reception SINR obtainable when the eNB uses PMI.

In an advanced system such as an LTE-A system, a method for obtainingadditional multi-user diversity using multi-user MIMO (MU-MIMO) wasadded. Higher accuracy is required in terms of channel feedback. Sincean interference channel exists between UEs multiplexed in an antennadomain in MU-MIMO, the accuracy of CSI may significantly affectinterference with other multiplexed UEs as well as a UE for performingfeedback. Accordingly, in an LTE-A system, in order to increase accuracyof a feedback channel, a final PMI has been determined to be separatelydesigned as a long-term and/or wideband PMI, W1, and a short-term and/orsubband PMI, W2.

The eNB can transform a codebook using a long-term covariance matrix ofa channel as shown in Equation 4 below as an example of a hierarchicalcodebook transformation method configuring one final PMI from two typesof channel information such as W1 and W2.

W=norm(W1W2)   [Equation 4]

In Equation 4, W1 (that is, long-term PMI) and W2 (that is, short-termPMI) denote codewords of a codebook generated in order to reflectchannel information, W denotes a codeword of a final transformedcodebook, and norm(A) denotes a matrix obtained by normalizing the normof each column of a matrix A to 1.

In Equation 4, the structures of W1 and W2 are shown in Equation 5below.

$\begin{matrix}{{{W\; 1(i)} = \begin{bmatrix}X_{i} & 0 \\0 & X_{i}\end{bmatrix}},{{{where}\mspace{14mu} X_{i}\mspace{14mu} {is}\mspace{14mu} {{Nt}/2}\mspace{14mu} {by}\mspace{14mu} M\mspace{14mu} {{matrix}.\text{}W}\; 2(j)} = {\overset{\overset{r\mspace{14mu} {columns}}{}}{\begin{bmatrix}e_{M}^{k} & e_{M}^{l} & e_{M}^{m} \\{\alpha_{j}e_{M}^{k}} & {\beta_{j}e_{M}^{l}} & {\gamma_{j}e_{M}^{m}}\end{bmatrix}}( {{{if}\mspace{14mu} {rank}} = r} )}},{{{where}\mspace{14mu} 1} \leq k},l,{m \leq {M\mspace{14mu} {and}\mspace{14mu} k}},l,{m\mspace{14mu} {are}\mspace{14mu} {{integer}.}}} & \lbrack {{Equation}\mspace{14mu} 5} \rbrack\end{matrix}$

The codeword structures of W1 and W2 shown in Equation 5 are designed byreflecting correlation characteristics of the channel generated when across-polarized antenna is used and a gap between antennas is narrow(e.g., a distance between adjacent antennas is equal to or less thanhalf a signal wavelength).

The cross-polarized antennas may be divided into a horizontal antennagroup and a vertical antenna group. At this time, each antenna group hasa uniform linear array (ULA) antenna property and two antenna groups areco-located. Accordingly, the correlations between antennas in each grouphave the same linear phase increment property and the correlationbetween the antenna groups has a phase rotation property.

Since a codebook is a value obtained by quantizing radio channels, acodebook may be designed by reflecting the characteristics of a channelcorresponding to a source without change. Equation 6 below shows anexample of a rank-1 codeword designed using the structures of Equations4 and 5, for convenience of description. Referring to Equation 6, it canbe seen that such channel properties are reflected to the codewordsatisfying Equation 4.

$\begin{matrix}{{W\; 1(i)^{*}W\; 2(j)} = \begin{bmatrix}{X_{i}(k)} \\{\alpha_{j}{X_{i}(k)}}\end{bmatrix}} & \lbrack {{Equation}\mspace{14mu} 6} \rbrack\end{matrix}$

In Equation 6, a codeword is expressed as an N_(t) (that is, the numberof transmit antennas)×1 vector. At this time, Equation 6 is composed ofan upper vector X_(i)(k) and a lower vector α_(j)X_(i)(k), whichrespectively represent the correlation characteristics of the horizontaland vertical antenna groups. At this time, X_(i)(k) is expressed as avector having the linear phase increment property by reflecting thecorrelation characteristics between antenna groups. A representativeexample thereof includes a discrete Fourier transform (DFT) matrix.

In addition, higher channel accuracy is necessary for CoMP. For example,CoMP joint transmission (JP) may be theoretically regarded as a MIMOsystem in which antennas are geographically distributed, because severaleNBs cooperatively transmit the same data to a specific UE. That is,even when MU-MIMO is implemented in JT, very high channel accuracy isrequired to avoid interference between UEs scheduled together, similarlyto single cell MU-MIMO operation. Even in CoMP coordinated beamforming(CB), precise channel information is required to avoid interference witha serving cell caused by a neighbor cell.

3.3 UE Operation for CSI Reporting

Time and frequency resources used by the UE to report CSI including CQI,PMI, precoding type indicator (PTI) and/or RI are scheduled by the eNB.For spatial multiplexing (SM), the UE shall determine RI correspondingto the number of transmission layers. For transmit diversity, the UEsets RI to 1.

A UE in transmission mode 8 or 9 is configured with or without PMI/RIreporting by a higher layer parameter pmi-RI-report. A UE is configuredwith resource-restricted CSI measurements if subframe sets C_(CSI,0) andC_(CSI,1) are configured by a higher layer.

When a UE is configured with one or more serving cells, the UE performsa CSI reporting only for activated serving cells. When the UE is notconfigured for simultaneous PUSCH and PUCCH transmission, the UEperiodically performs CSI reporting on the PUCCH in the subframe with noPUSCH allocation. When the UE is not configured for simultaneous PUSCHand PUCCH transmission, the UE performs periodic CSI reporting in asubframe to which the PUSCH of a serving cell having a smallest servingcell index ServCellIndex is allocated. At this time, the UE uses thesame format as the PUCCH-based periodic CSI reporting format on thePUSCH. Under a predetermined condition, the UE transmits periodic CSIreporting on the PUSCH. For example, for aperiodic CQI/PMI reporting, RIreporting is transmitted only when the configured CSI feedback typesupports RI reporting.

In addition, even when the UE periodically performs CSI reporting, theUE may aperiodically perform CSI reporting when UL grant, in which a CSIrequest field is set, is received from the eNB.

3.3.1 Aperiodic CSI Reporting using PUSCH

The UE performs aperiodic CSI reporting using the PUSCH in a subframen+k, upon receiving an uplink DCI format (that is, UL grant) or randomaccess response grant, in which a CSI request field is set, in asubframe n of a serving cell c. When the CSI request field has 1 bit andis set to “1”, the CSI reporting request is triggered for the servingcell c. When the CSI request field has 2 bits, the CSI reporting requestis triggered according to Table 17 below.

TABLE 17 Value of CSI request field Description ‘00’ No aperiodic CSIreport is triggered ‘01’ Aperiodic CSI report is triggered for servingcell c ‘10’ Aperiodic CSI report is triggered for a 1^(st) set ofserving cells configured by higher layers ‘11’ Aperiodic CSI report istriggered for a 2^(nd) set of serving cells configured by higher layers

In Table 17, the CSI request field set to “00” indicates that noaperiodic CSI report is triggered, “01” indicates that the aperiodic CSIreport is triggered for the serving cell c, “10” indicates that theaperiodic CSI report is triggered for a first set of serving cellsconfigured by higher layers, and “11” indicates that the aperiodic CSIreport is triggered for a second set of serving cells configured byhigher layers.

A UE is not expected to receive more than one aperiodic CSI reportrequest for a given subframe.

[Table 18] below lists reporting modes for CSI transmission on a PUSCH.

TABLE 18 PMI feedback type Single Multiple No PMI PMI PMI PUSCH WidebandMode 1-2 CQI (wideband CQI) feedback UE Selected Mode 2-0 Mode 2-2 type(subband CQI) Higher Layer- Mode 3-0 Mode 3-1 configured (subband CQI)

Reporting modes listed in [Table 18] are selected by a higher layer, anda CQI, a PMI, and an RI are transmitted in the same PUSCH subframe. Adetailed description will be given of each reporting mode.

1-1) Mode 1-2

A UE selects a precoding matrix for each subband on the assumption thatdata is transmitted only in the subband. The UE generates CQI on theassumption of a previously selected precoding matrix for a system bandor all bands (set S) indicated by the higher layer. Further, the UEtransmits the CQI and a PMI for each subband. Herein, the size of eachsubband may vary with the size of the system band.

1-2) Mode 2-0

The UE selects M preferred subbands for a system band or a band (set S)indicated by the higher layer. The UE generates one CQI on theassumption that data is transmitted in the selected M subbands. The UEadditionally generates one wideband CQI for the system band or the setS. If there are a plurality of codewords for the selected M subbands,the UE defines a CQI for each codeword as a differential value. Herein,differential CQIs are set to values obtained by subtracting a windebandCQI index from indexes corresponding to CQIs for the selected Msubbands.

The UE transmits information about the positions of the selected Msubbands, one CQI for the selected M subbands, and a CQI for the totalband or the set S. Herein, the size of a subband and M may vary with thesize of the system band.

1-3) Mode 2-2

The UE simultaneously selects the positions of M preferred subbands anda single precoding matrix for the M preferred subbands on the assumptionthat data is transmitted in the M preferred subbands. Herein, a CQI isdefined per codeword for the M preferred subbands.

The UE additionally generates a wideband CQI for the system band or theset S.

The UE transmits information about the positions of the M preferredsubbands, one CQI for the M selected subbands, a single precoding matrixindex for the M preferred subbands, a wideband precoding matrix index,and a wideband CQI. Herein, the size of a subband and M may vary withthe size of the system band.

1-4) Mode 3-0

The UE generates and reports a windeband CQI.

The UE generates a CQI for each subband on the assumption that data istransmitted in the subband. Herein, even though an RI>1, a CQIrepresents only a CQI value for a first codeword.

1-5) Mode 3-1

The UE generates a single precoding matrix for the system band or theset S.

The UE generates a subband CQI per codeword on the assumption of apreviously generated single precoding matrix for each subband.

The UE generates a wideband CQI on the assumption of a single precodingmatrix. Herein, a CQI for each subband is expressed as a differentialvalue. For example, a subband CQI is defined as a value obtained bysubtracting a wideband CQI index from a subband CQI index (SubbandCQI=subband CQI index−wideband CQI index). Also, the size of a subbandmay vary with the size of the system band.

4. CSI Feedback Method of MTC UE

4.1 MTC UE

Machine type communication (MTC) means communication between machineswithout human intervention. MTC may bring various services and, as aresult, may diversify terminals. At present, an MTC service consideredas most promising is smart metering. A smart meter is at once ameasurement device that measures the amount of used electricity, water,gas, or the like and a transmission device that transmits various typesof information over a communication network.

For example, the smart meter periodically or aperiodically transmits theamount of used electricity, water, or gas to a management center througha communication network. The communication network may use a licensedband like a cellular network or an unlicensed band like a Wi-Fi network.The present invention considers MTC over an LTE cellular network.

In an MTC service such as smart metering, an MTC UE should transmit datato a BS periodically. Although a data transmission period may vary withsettings of a service provider, it is assumed that the data transmissionperiod is very long. Since an MTC UE generally performs only arelatively simple function in many cases, there is a need forimplementing the MTC UE economically.

Therefore, the buffer capacity and decoding complexity of an MTC UE maybe reduced by restricting a receivable bandwidth of the MTC UEirrespective of a system bandwidth. The present invention proposes a CSIfeedback method in the case where the receivable bandwidth of a UE isrestricted.

The below-described MTC UE is a low-cost low-power terminal and issimply referred to as “UE” for convenience of description. That is, inthe embodiments of the present invention, unless otherwise stated, theUE means a low-cost MTC UE. In addition, a bandwidth supported in alegacy system may be referred to as a legacy bandwidth (or a firstbandwidth) and a bandwidth having a limited size allocated to an MTC UEmay be referred to as an MTC bandwidth (or a second bandwidth).

4.2 Method for Restricting Bandwidth of a Low-Cost MTC UE

There are two methods for restricting the receivable bandwidth of a UE.One of the methods is that a limited frequency area of a systembandwidth is semi-statically allocated to a UE using a higher layersignal (RRC) or an SIBx message. The other method is that an availablebandwidth is indicated to a UE as control information through aPDCCH/EPDCCH. This method restricts the number of allocated RBs duringresource allocation.

4.3 CSI Feedback in the Case where Bandwidth of a UE is Semi-StaticallyRestricted

Hereinafter, methods of semi-statically allocating a specific frequencyarea within the system bandwidth as the above-described first methodwill be described.

The specific frequency area may be allocated as system information suchas an SIB. Since it is expected that the size of data used by a low-costMTC UE is very small in consideration of an application such as smartmetering, the number of RBs for bandwidth used by the UE fortransmission/reception may be restricted. For example, in a legacysystem such as an LTE/LTE-A system, a legacy bandwidth may be composedof up to 110 RBs. However, the MTC UE may be configured to restrict theMTC bandwidth to a predetermined area (e.g., about 6 RBs).

As one aspect of the present invention, since the number of RBsreceivable by the low-cost MTC UE is remarkably less than that of RBsreceivable by the legacy UE, the UE may be configured to perform CSIfeedback with respect to wideband CQI/wide band PMI only and not tosupport subband CQI/subband PMI.

At this time, the concept of W-CQI/W-PMI and S-CQI/S-PMI transmitted bythe MTC UE is different from W-CQI/W-PMI and S-CQI/S-PMI of the legacysystem. For example, the W-CQI/W-PMI transmitted by the MTC UE meansCQI/PMI of a total band for the MTC bandwidth semi-statically allocatedto a UE, such as an SIB, not CQI/PMI of a total band for a legacybandwidth supported in a wireless access system. Hereinafter, theW-CQI/W-PMI used in the legacy system is referred to as legacyW-CQI/legacy W-PMI or first W-CQI/first W-PMI and the W-CQI/W-PMI forthe MTC UE is referred to as MTC W-CQI/MTC W-PMI or second W-CQI/secondW-PMI. For example, 6 RBs may be set as a total band in the case of theMTC W-PMI, but up to 100 RBs may be set as a total band in the case ofthe legacy W-PMI.

Since it is difficult to provide a plurality of antennas to a low-costMTC UE, the low-cost MTC UE preferably does not support spatialmultiplexing (SM). Accordingly, the W-PMI is preferably limited to arank-1 PMI.

Hereinafter, an aperiodic CSI feedback method and a periodic CSIfeedback method in a case where a bandwidth of a UE is semi-staticallyrestricted will be described.

4.3.1 Aperiodic CSI feedback method-1

In a legacy system, aperiodic CSI feedback is not supported for a systembandwidth of 7 or fewer RBs. However, in a system supporting MTC,although the system bandwidth may be 7 or more RBs, aperiodic CSIfeedback is not preferably supported even when the restricted bandwidthof the MTC UE can be limited to 7 or below. This is because the low-costMTC UE preferably minimizes power consumption by periodicallytransmitting data and operating in idle mode during the remaining timeperiod, and thus CSI feedback is requested only when the BS needs it,which is an advantage of aperiodic CSI feedback.

Referring to Table 18, the aperiodic CSI feedback transmitted in thelegacy system may support a mode for transmitting UE selected subbandCQI (mode 2-0) and a mode for transmitting higher layer configuredsubband CQI (mode 3-0, and mode 3-1). However, the low-cost MTC UEpreferably does not support subband CQI and transmits widebandCQI/wideband PMI for a limited frequency area irrespective of a systembandwidth.

That is, the low-cost MTC UE transmits, to a BS, legacy W-CQI for atotal system bandwidth, MTC W-CQI and MTC W-PMI (when needed) for alimited bandwidth allocated to the MTC UE.

If the MTC UE is configured not to report subband CQI to the BS in a UEselected mode (mode 2-0 or mode 2-2) or a higher layer configured mode(e.g., mode 3-0 or mode 3-1) or is configured not to support the modes,the MTC UE does not need to transmit information about a labelindicating the position of a subband and information about differentialCQI. Accordingly, it is possible to reduce feedback overhead of the CSIto be transmitted by the low-cost MTC UE. In addition, in the case ofthe low-cost MTC UE, second W-CQI for the limited number of RBs isdefined as a differential CQI value with respect to first W-CQI for thetotal system bandwidth, the feedback overhead can be further reduced.

4.3.2 A Periodic CSI Feedback Method-2

As a method different from section 4.3.1, the low-cost MTC UE may beconfigured to support subband CQI feedback. At this time, a subband sizeis determined on the assumption that the limited number of RBs allocatedto the low-cost MTC UE is a system bandwidth, instead of the systembandwidth of the legacy system.

Table 19 below illustrates an embodiment of subband sizes for higherlayer configured subband CQI feedback modes (mode 3-0 and mode 3-1)newly configured in a low-cost MTC UE.

TABLE 19 System bandwidth allocated Subband size to MTC UE (PRB) (numberof RBs) 6-7 4  8-10 4 11-26 4 27-63 6  64-110 8

Table 20 below illustrates an embodiment of subband sizes for UEselected subband CQI feedback modes (mode 2-0 and mode 2-2) newlyconfigured in a low-cost MTC UE.

TABLE 20 Limited number of PRBs allocated to Subband size M low-cost MTC(number of RBs) (number of subbands) 6-7 2 1  8-10 2 1 11-26 2 3 27-63 35  64-110 4 8

In Tables 19 and 20, the limited system bandwidth allocated to the MTCUE may be defined as a subband size. That is, the aperiodic CSI feedbackmethod when the subband CQI is not configured in the low-cost MTC UE isdescribed in section 4.3.1 and the case where the subband CQI issupported within the bandwidth of the MTC UE is described in section4.3.2.

When a limited number of RBs is allocated to the UE in section 4.3.2,the start of a subband is aligned with the start of the bandwidth of theMTC UE (the limited number of RBs allocated to the UE). That is, if thestart of the subband is always aligned with the start of the limitednumber of RBs allocated to the UE, the boundary of the subband is alwaysaligned with the boundary of the limited number of RBs allocated to theUE. Otherwise, since the boundary of the subband is not aligned with theboundary of the limited number of RBs allocated to the UE, the bandwidthof the MTC UE may be allocated from the middle of the subband. In thiscase, since the MTC should perform calculation and transmission ofsubband CQI twice, burden of the UE on complexity and calculation canincrease.

4.3.3 Periodic CSI Feedback Method

Referring to Table 16, in the periodic CSI feedback method used in thelegacy system, legacy W-CQI and subband CQI may be transmitted.

In the embodiment of the present invention, an MTC UE may be configuredto further transmit legacy W-CQI for a total system bandwidth inperiodic CSI feedback and MTC W-CQI for a limited number of RBsallocated to the MTC UE and MTC W-PMI if necessary. At this time, theMTC W-CQI may be defined as differential CQI with legacy W-CQI for atotal system bandwidth. Accordingly, even when the MTC transmits legacyW-CQI (that is, first W-CQI) and MTC W-CQI (that is, second W-CQI), itis possible to reduce feedback overhead. In this case, the MTC UE may beconfigured not to transmit subband CQI.

Alternatively, if the MTC UE periodically performs CSI feedback, onlyMTC W-CQI for a limited bandwidth allocated to the MTC UE may be fedback to the BS.

As another aspect of the present invention, the MTE UE may support mode2-0 and mode 2-1 which are the periodic CSI reporting modes even in asystem bandwidth of 7 or fewer RBs as in section 4.3.1. At this time, asubband size and the number of bandwidth parts (BTs) may be determinedaccording to the limited number of RBs allocated to the low-cost MTC UE,not according to the system bandwidth. That is, the MTC UE may reportthe limited bandwidth allocated to the MTC UE to the BS as subband CQIin addition to the legacy MTC W-CQI.

Table 21 below shows an embodiment of a subband size and the number ofBTs when UE selected subband CQI feedback is supported in periodic CSIfeedback.

TABLE 21 Bandwidth of low-cost Subband size MTC UE (number of PRBs)(number of RBs) Bandwidth part 6-7 4 1  8-10 4 1 11-26 4 2 27-63 6 3 64-110 8 4

FIG. 17 is a diagram showing a process of performing the methodsdescribed in section 4.3.

Referring to FIG. 17, an MTC UE may receive a system bandwidth having alimited size allocated to the MTC UE from a serving cell including a BSthrough an SIBx message (S1710).

That is, the system bandwidth for MTC operation may be semi-staticallyallocated to the MTC UE in step S1710 to transmit and receive a PDSCH, aPUSCH, etc. within the bandwidth. In another aspect of the presentinvention, step S1710 may not be performed. For example, the limitedsystem bandwidth which may be used by the MTC UE in the system may bepredetermined. In this case, the MTC UE may decode only the limitedsystem bandwidth.

When the MTC UE is allocated the system bandwidth (RB units) having thelimited size, CSI including at least one of legacy W-CQI, MTC W-CQI andMTC W-PMI may be calculated (S1720).

Alternatively, even when the bandwidth having the limited size isallocated to the MTC UE, a subband may be used. For example, in stepS1710, the MTC UE may be allocated a subband used for MTC through anSIBx message. In this case, the MTC UE may calculate legacy W-CQI andsubband CQI in step S1720. In this case, for information such as subbandsize, M and BT for calculating the subband CQI, refer to Tables 19, 20and 21.

Thereafter, the MTC UE may periodically or aperiodically report the MTCW-CQI or subband CQI calculated in step S1720 to the BS (S1730).

For the periodic or aperiodic CSI reporting method used in step S1730,refer to sections 3 and 4.3.

4.4 CSI Feedback Method in a Case where a Bandwidth of a UE isDynamically Restricted

Hereinafter, methods of dynamically allocating a specific frequency areato an MTC UE within a system bandwidth through a control channel will bedescribed.

4.4.1 Aperiodic CSI Feedback Method

As an aspect of the present invention, an MTC UE may be configured tomake the best use of a legacy CSI reporting mode. Only MTC W-CQI/MTCW-PMI (if necessary) is configured to be transmitted for the limitednumber of RBs allocated to the MTC UE.

For example, if the bandwidth of the MTC UE is dynamically allocatedthrough a PDCCH or an EPDCCH, the MTC UE may receive an aperiodic CSIfeedback request through the PDCCH or the EPDCCH. At this time, the MTCUE may periodically report the legacy W-CQI and the MTC W-CQI for thelimited bandwidth allocated through PDCCH to the BS.

As another aspect of the present invention, in the case of mode 3-0 andmode 3-1 which are higher layer configured modes, the subband size maybe limited to the limited number of RBs for the MTC UE regardless of thesystem bandwidth. For example, in the case of mode 2-0 which is a UEselected mode, M=1 may be set and the subband size may be set to thelimited number of RBs regardless of the system bandwidth allocated tothe MTC UE.

That is, the BS may dynamically allocate the bandwidth of the MTC UEthrough a PDCCH or an EPDCCH. At this time, the bandwidth allocated tothe MTC UE may be the limited number of RBs regardless of the systembandwidth as a subband bandwidth. When the MTC UE receives a request foraperiodic CSI feedback, legacy W-CQI and subband CQI for the allocatedsubbands may be reported to the BS.

4.4.2 Periodic CSI Feedback Method

The below-described embodiments of the present invention relate to amethod of setting a subband size to a limited number of RBs regardlessof a system bandwidth in mode 2-0 and mode 2-1 which are the UE selectedmodes. For example, a bandwidth part (BT) is set to a value obtained bydividing the system bandwidth by the limited number of RBs, such thatthe UE is always allocated the limited number of RBs. That is, the MTCUE may transmit a CQI value for a subband dynamically allocated by theBS in a CSI reporting period in the UE selected mode. For example, ifthe system bandwidth is 50 RBs and the limited number of RBs allocatedto the UE is 6 RBs, the BT may be set to 9. Accordingly, the UE maytransmit a CQI value for 6 RBs in every reporting period.

FIG. 18 is a diagram showing a process of performing the methodsdescribed in section 4.4.

Referring to FIG. 18, an MTC UE may receive a system bandwidth having alimited size, which is dynamically allocated by a serving cell includinga BS, through a PDCCH and/or an EPDCCH in every subframe (S1810).

That is, the MTC UE is dynamically allocated the system bandwidth forMTC operation in step S1810, the MTC UE may transmit and receive a PDSCHor PUSCH within the bandwidth.

In addition, if the MTC UE is allocated the system bandwidth having alimited size (RB units), CSI including at least one of W-CQI, MTC W-CQIand MTC W-PMI may be calculated (S1820).

Alternatively, even when the MTC UE is allocated the bandwidth havingthe limited size, a subband may be used. For example, in step S1810, theMTC UE may be allocated a subband to be used for MTC through an SIBxmessage. In this case, the MTC UE may calculate legacy W-CQI and subbandCQI in step S1820.

Thereafter, the MTC UE may periodically or aperiodically report the MTCW-CQI or the subband CQI calculated in step S1820 to the BS (S1830).

For the periodic or aperiodic CSI reporting method used in step S1830,refer to sections 3 and 4.3.

5. Apparatuses

Apparatuses illustrated in FIG. 19 are means that can implement themethods described before with reference to FIGS. 1 to 18.

A UE may act as a transmission end on a UL and as a reception end on aDL. An eNB may act as a reception end on a UL and as a transmission endon a DL.

That is, each of the UE and the eNB may include a Transmitter (Tx) 1940or 1950 and a Receiver (Rx) 1960 or 1970, for controlling transmissionand reception of information, data, and/or messages, and an antenna 1900or 1910 for transmitting and receiving information, data, and/ormessages.

Each of the UE and the eNB may further include a processor 1920 or 1930for implementing the afore-described embodiments of the presentdisclosure and a memory 1980 or 1990 for temporarily or permanentlystoring operations of the processor 1920 or 1930.

The embodiments of the present invention may be performed using theabove-described components and functions of the UE and the BS. Forexample, the processor of the BS may allocate a system bandwidth havinga limited size to an MTC UE for MTC operation, by combining the methodsdisclosed in sections 1 to 4. At this time, the system bandwidth havingthe limited size may be allocated and managed independently of a legacysystem bandwidth for a normal UE, that is, a legacy UE. A process ofallocating the system bandwidth having the limited size to the MTC UEmay be semi-statically or dynamically performed. For a detaileddescription thereof, refer to section 4. In addition, the processor ofthe MTC UE may calculate MTC W-CQI for an MTC system bandwidth having alimited size allocated to the MTC UE, by combining the descriptions ofsections 1 to 4. At this time, the MTC UE may also calculate legacyW-CQI in order to apply a link with a PDCCH and report the legacy W-CQIto the BS along with MTC W-CQI. For a detailed description thereof,refer to section 4. The processors of the MTC UE and the BS may use atransmitter and a receiver in order to support such operation.

The transmitter and the receiver of the UE and the eNB may perform apacket modulation/demodulation function for data transmission, ahigh-speed packet channel coding function, OFDMA packet scheduling, TDDpacket scheduling, and/or channelization. Each of the UE and the eNB ofFIG. 19 may further include a low-power Radio Frequency(RF)/Intermediate Frequency (IF) module.

Meanwhile, the UE may be any of a Personal Digital Assistant (PDA), acellular phone, a Personal Communication Service (PCS) phone, a GlobalSystem for Mobile (GSM) phone, a Wideband Code Division Multiple Access(WCDMA) phone, a Mobile Broadband System (MBS) phone, a hand-held PC, alaptop PC, a smart phone, a Multi Mode-Multi Band (MM-MB) terminal, etc.

The smart phone is a terminal taking the advantages of both a mobilephone and a PDA. It incorporates the functions of a PDA, that is,scheduling and data communications such as fax transmission andreception and Internet connection into a mobile phone. The MB-MMterminal refers to a terminal which has a multi-modem chip built thereinand which can operate in any of a mobile Internet system and othermobile communication systems (e.g. CDMA 2000, WCDMA, etc.).

Embodiments of the present disclosure may be achieved by various means,for example, hardware, firmware, software, or a combination thereof.

In a hardware configuration, the methods according to exemplaryembodiments of the present disclosure may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the methods according to theembodiments of the present disclosure may be implemented in the form ofa module, a procedure, a function, etc. performing the above-describedfunctions or operations. A software code may be stored in the memory1980 or 1990 and executed by the processor 1920 or 1930. The memory islocated at the interior or exterior of the processor and may transmitand receive data to and from the processor via various known means.

Those skilled in the art will appreciate that the present disclosure maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent disclosure. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein. It is obvious to those skilled in the art thatclaims that are not explicitly cited in each other in the appendedclaims may be presented in combination as an embodiment of the presentdisclosure or included as a new claim by a subsequent amendment afterthe application is filed.

INDUSTRIAL APPLICABILITY

The present disclosure is applicable to various wireless access systemsincluding a 3GPP system, a 3GPP2 system, and/or an IEEE 802.xx system.Besides these wireless access systems, the embodiments of the presentdisclosure are applicable to all technical fields in which the wirelessaccess systems find their applications.

1. A method for reporting channel status information (CSI) at a machinetype communication (MTC) user equipment (UE) in a wireless access systemsupporting a MTC, the method comprising: receiving, from an enhancedNode B (eNB), a higher layer signal configuring a CSI report mode to theMTC UE; receiving, from the eNB, allocation information indicatingrestricted bandwidth allocated to the MTC UE; calculating the CSI forthe restricted bandwidth based on the CSI report mode; and reporting theCSI to the eNB, wherein the CSI includes a wideband channel statusinformation (W-CQI) valve for the restricted bandwidth except for UEselected subband status information, even though the CSI report mode isconfigured as a mode 2-0 representing a UE selected subband CQIfeedback, and wherein a size of the restricted bandwidth is 6 resourceblocks and the wideband CQI value is calculated conditioned on rank 1.2. The method according to claim 1, the UE selected subband statusinformation is associated with one or more subbands, and the UE selectedsubband status information includes a label information indicating aposition of a subband and information indicating differential CQI. 3.The method according to claim 1, wherein the allocation information isdynamically transmitted in every subframe through a physical downlinkcontrol channel (PDCCH) or an enhanced physical downlink control channel(EPDCCH).
 4. The method according to claim 1, wherein the CSI isaperiodically transmitted via a physical uplink shared channel (PUSCH)to the eNB when an aperiodic CSI report has been requested.
 5. Themethod according to claim 1, wherein the CSI is periodically transmittedvia a physical uplink control channel (PUCCH).
 6. A machine typecommunication (MTC) user equipment (UE) for reporting channel statusinformation (CSI) in a wireless access system supporting MTC, the MTC UEcomprising: a transmitter; a receiver; and a processor configured tocontrol the transmitter and the receiver to support feedback of the CSI,wherein the processor is configured to: control the receiver to receivea higher layer signal configuring a CSI report mode to the MTC UE froman enhanced Node B (eNB), control the receiver to receive, from the eNB,allocation information indicating restricted bandwidth allocated to theMTC UE; calculate the CSI for the restricted bandwidth based on the CSIreport mode; and control the transmitter to report the CSI to the eNB,wherein the CSI includes a wideband channel status information (W-CQI)value for the restricted bandwidth except for UE selected subband statusinformation, even though the CSI report mode is configured as a mode 2-0representing a UE selected subband CQI feedback, and wherein a size ofthe restricted bandwidth is 6 resource blocks and the wideband CQI valueis calculated conditioned on rank
 1. 7. The MTC UE according to claim 6,wherein the UE selected subband status information is associated withone or more subbands, and the UE selected subband status informationincludes a label information indicating a position of a subband andinformation indicating differential CQI.
 8. The MTC UE according toclaim 6, wherein the allocation information is dynamically transmittedin every subframe through a physical downlink control channel (PDCCH) oran enhanced physical downlink control channel (EPDCCH).
 9. The MTC UEaccording to claim 6, wherein the processor aperiodically feeds back theCSI via a physical uplink shared channel (PUSCH) to the eNB when anaperiodic CSI report has been requested.
 10. The MTC UE according toclaim 6, wherein the processor periodically feeds back the CSI via aphysical uplink control channel (PUCCH).